Respostas e perguntas da avaliação de habilidades do LinkedIn - JavaScript

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Link de avaliação(Linkedin)

T1. Qual operador retorna verdadeiro se os dois valores comparados não forem iguais?

<>
~
==!
!==

Operadores de comparação Javascript de referência

Q2. Como uma instrução forEach é diferente de uma instrução for?

Apenas uma instrução for usa uma função de retorno de chamada.
Uma instrução for é mais genérica e pode ser usada com vários objetos iteráveis, enquanto uma instrução forEach é projetada principalmente para arrays, mas também pode ser usada com outros objetos iteráveis, como Sets.
Somente uma instrução forEach permite especificar seu próprio iterador.
Uma instrução forEach é genérica, mas uma instrução for pode ser usada apenas com um array.

Diferenças de referência entre forEach e for loop

3º T. Revise o código abaixo. Qual instrução chama a função addTax e passa 50 como um argumento?

function addTax(total) {
  return total * 1.05;
}

addTax = 50;
return addTax 50;
addTax(50);
addTax 50;

Funções de referência em javascript

Q4. Qual afirmação é a maneira correta de criar uma variável chamada taxa e atribuir-lhe o valor 100?

let rate = 100;
let 100 = rate;
100 = let rate;
rate = 100;

Operadores de atribuição Javascript de referência

Q5. Qual instrução cria um novo objeto usando o construtor Person? Qual instrução cria um novo objeto Person chamado “aluna”?

var student = new Person();
var student = construct Person;
var student = Person();
var student = construct Person();

Referência

Q6. Quando a instrução final no código mostrado seria registrada no console? Quando os ‘resultados mostrados’ estar logado no console?

let modal = document.querySelector('#result');
setTimeout(function () {
  modal.classList.remove('hidden');
}, 10000);
console.log('Results shown');

depois 10 é importante entender por que esses animais passaram a ser parte integrante da identidade canadense
depois que os resultados são recebidos da solicitação HTTP
depois 10000 segundos
imediatamente

Referência Javascript é síncrono e de thread único

Q7. Qual trecho você poderia adicionar a este código para imprimir “Comida” para a consola?

class Animal {
  static belly = [];
  eat() {
    Animal.belly.push('food');
  }
}
let a = new Animal();
a.eat();
console.log(/* Snippet Here */); //Prints food

a.prototype.belly[0]
Object.getPrototype0f (a).belly[0]
Animal.belly[0]
a.belly[0]

Palavra-chave estática da classe Javascript de referência

Q8. Você escreveu o código mostrado para registrar um conjunto de valores consecutivos, mas em vez disso resulta no valor 5, 5, 5, e 5 sendo logado no console. Qual versão revisada do código resultaria no valor 1, 2, 3 e 4 sendo logado?

for (var i = 1; i <= 4; i++) {
  setTimeout(function () {
    console.log(i);
  }, i * 10000);
}

for (var i = 1; i <= 4; i++) {
  (function (i) {
    setTimeout(function () {
      console.log(j);
    }, j * 1000);
  })(j);
}

for (var i = 1; i <= 4; i++) {
  setTimeout(function () {
    console.log(i);
  }, i * 1000);
}

for (var i = 1; i <= 4; i++) {
  (function (j) {
    setTimeout(function () {
      console.log(j);
    }, j * 1000);
  })(i);
}

for (var j = 1; j <= 4; j++) {
  setTimeout(function () {
    console.log(j);
  }, j * 1000);
}

Q9. Como uma função cria um fechamento?

Recarrega o documento sempre que o valor muda.
Ele retorna uma referência a uma variável em seu escopo pai.
Conclui a execução sem retornar.
Copia uma variável local para o escopo global.

Referência

Q10. Qual instrução cria uma nova função chamada descontoPreço?

let discountPrice = function (price) {
  return price * 0.85;
};

let discountPrice(price) {
  return price * 0.85;
};

let function = discountPrice(price) {
  return price * 0.85;
};

discountPrice = function (price) {
  return price * 0.85;
};

Referência que define funções javascript

Q11. Qual é o resultado no console da execução do código mostrado?

var Storm = function () {};
Storm.prototype.precip = 'rain';
var WinterStorm = function () {};
WinterStorm.prototype = new Storm();
WinterStorm.prototype.precip = 'snow';
var bob = new WinterStorm();
console.log(bob.precip);

Tempestade()
indefinido
'chuva’
'neve’

Cadeia de protótipos de referência

Q12. Você precisa corresponder a um valor de tempo como 12:00:32. Qual das seguintes expressões regulares funcionaria para o seu código?

/[0-9]{2,}:[0-9]{2,}:[0-9]{2,}/
/\d\d:\d\d:\d\d/
/[0-9]+:[0-9]+:[0-9]+/
/ : : /

NOTA: Os três primeiros estão parcialmente corretos e corresponderão aos dígitos, mas o segunda opção é a mais correta porque vai só Combine 2 dígito valores de tempo (12:00:32). A primeira opção teria funcionado se o intervalo de repetições parecesse [0-9]{2}, porém por causa do vírgula [0-9]{2,} ele irá selecionar 2 ou mais dígitos (120:000:321). A terceira opção será qualquer intervalo de dígitos de tempo, solteiro e múltiplo (significado 1:2:3 também combinará).

Mais recursos:

Q13. Qual é o resultado no console da execução deste código?

'use strict';
function logThis() {
  this.desc = 'logger';
  console.log(this);
}
new logThis();

undefined
window
{desc: "logger"}
function

Classes javascript de referência

Q14. Como você faria referência ao texto ‘avenida’ no código mostrado?

let roadTypes = ['street', 'road', 'avenue', 'circle'];

roadTypes.2
tipos de estradas[3]
roadTypes.3
tipos de estradas[2]

Referência de acesso a arrays javascript

Q15. Qual é o resultado da execução desta declaração?

console.log(typeof 42);

'float'
'value'
'number'
'integer'

Referência a tipos de dados javascript

Q16. Qual propriedade faz referência ao objeto DOM que despachou um evento?

self
object
target
source

Referência a eventos DOM

Q17. Você está adicionando tratamento de erros ao código mostrado. Qual código você incluiria na instrução if para especificar uma mensagem de erro?

function addNumbers(x, y) {
  if (isNaN(x) || isNaN(y)) {
  }
}

exception('One or both parameters are not numbers')
catch('One or both parameters are not numbers')
error('One or both parameters are not numbers')
throw('One or both parameters are not numbers')

Referência de lançamento de javascript

Q18. Qual método converte dados JSON em um objeto JavaScript?

JSON.fromString();
JSON.parse()
JSON.toObject()
JSON.stringify()

Referência converter json para objeto javascript

Q19. Quando você usaria uma declaração condicional?

Quando você deseja reutilizar um conjunto de instruções várias vezes.
Quando você deseja que seu código escolha entre várias opções.
Quando você deseja agrupar dados.
Quando você deseja percorrer um grupo de instruções.

Referência a condicionais javascript

Q20. Qual seria o resultado no console da execução deste código?

for (var i = 0; i < 5; i++) {
  console.log(i);
}

1 2 3 4 5
1 2 3 4
0 1 2 3 4
0 1 2 3 4 5

Reference javascript for loops

Q21. Which Object method returns an iterable that can be used to iterate over the properties of an object?

Object.get()
Object.loop()
Object.each()
Object.keys()

Reference javascript object static methods

Q22. What will be logged to the console?

var a = ['dog', 'cat', 'hen'];
a[100] = 'fox';
console.log(a.length);

Q23. What is one difference between collections created with Map and collections created with Object?

You can iterate over values in a Map in their insertion order.
You can count the records in a Map with a single method call.
Keys in Maps can be strings.
You can access values in a Map without iterating over the whole collection.

Explicação: Map.prototype.size returns the number of elements in a Map, whereas Object does not have a built-in method to return its size. Reference map methods javascript

Q24. What is the value of dessert.type after executing this code?

const dessert = { type: 'pie' };
dessert.type = 'pudding';

pie
The code will throw an error.
pudding
indefinido

Reference working with js objects

Q25. 0 && Oi

ReferenceError
verdade
0
falso

Reference boolean logic

Q26. Which of the following operators can be used to do a short-circuit evaluation?

++
--
==
||

Reference short circuit javascript

Q27. Which statement sets the Person constructor as the parent of the Student constructor in the prototype chain?

Student.parent = Person;
Student.prototype = new Person();
Student.prototype = Person;
Student.prototype = Person();

Reference prototype object js

Q28. Why would you include a “use strict” statement in a JavaScript file?

to tell parsers to interpret your JavaScript syntax loosely
to tell parsers to enforce all JavaScript syntax rules when processing your code
to instruct the browser to automatically fix any errors it finds in the code
to enable ES6 features in your code

Reference what is use strict in js

Q29. Which Variable-defining keyword allows its variable to be accessed (as undefined) before the line that defines it?

all of them
const
var
let

Reference var vs let vs const in js

Q30. Which of the following values is not a Boolean false?

Boolean(0)
Boolean("")
Boolean(NaN)
Boolean("false")

Reference boolean of a string

Q31. Which of the following is not a keyword in JavaScript?

this
catch
function
array

Reference js reserved words

Q32. Which variable is an implicit parameter for every function in JavaScript?

Arguments
args
argsArray
argumentsList

Reference implicit js parameters for functions

Q33. For the following class, how do you get the value of 42 from an instance of X?

class X {
  get Y() {
    return 42;
  }
}
var x = new X();

x.get('Y')
x.Y
x.Y()
x.get().Y

Reference getters

Q34. What is the result of running this code?

sum(10, 20);
diff(10, 20);
function sum(x, y) {
  return x + y;
}

let diff = function (x, y) {
  return x - y;
};

30, ReferenceError, 30, -10
30, ReferenceError
30, -10
ReferenceError, -10

Reference accessing before initialization

Q35. Why is it usually better to work with Objects instead of Arrays to store a collection of records?

Objects are more efficient in terms of storage.
Adding a record to an object is significantly faster than pushing a record into an array.
Most operations involve looking up a record, and objects can do that better than arrays.
Working with objects makes the code more readable.

Reference efficiency of lookups Explicação: Records in an object can be retrieved using their key which can be any given value (por exemplo. an employee ID, a city name, etc), whereas to retrieve a record from an array we need to know its index.

Q36. Which statement is true about the “async” attribute for the HTML script tag?

It can be used for both internal and external JavaScript code.
It can be used only for internal JavaScript code.
It can be used only for internal or external JavaScript code that exports a promise.
It can be used only for external JavaScript code.

Reference async attribute for html

Q37. How do you import the lodash library making it top-level Api available as the “_” variable?

import _ from 'lodash';
import 'lodash' as _;
import '_' from 'lodash;
import lodash as _ from 'lodash';

Reference how to import library in js

Q38. What does the following expression evaluate to?

[] == [];

verdade
indefinido
[]
falso

Reference arrays in js are objects

Q39. What type of function can have its execution suspended and then resumed at a later point?

Generator function
Arrow function
Async/ Await function
Promise function

Reference what are generators in nodejs

Q40. What will this code print?

var v = 1;
var f1 = function () {
  console.log(v);
};

var f2 = function () {
  var v = 2;
  f1();
};

f2();

2
1
Nenhuma coisa – this code will throw an error.
indefinido

Reference closures in js / nested functions

Q41. Which statement is true about Functional Programming?

Every object in the program has to be a function.
Code is grouped with the state it modifies.
Date fields and methods are kept in units.
Side effects are not allowed.

Reference functional programming

Q42. Your code is producing the error: TypeError: Cannot read property ‘reduce’ of undefined. O que isso significa?

You are calling a method named reduce on an object that’s declared but has no value.
You are calling a method named reduce on an object that does not exist.
You are calling a method named reduce on an empty array.
You are calling a method named reduce on an object that has a null value.

Explicação: You cannot invoke reduce on undefined object... It will throw (yourObject is not Defined...)

Q43. How many prototype objects are in the chain for the following array?

let arr = [];

Reference array prototype

Q44. Which choice is não a unary operator?

typeof
delete
instanceof
void

Reference js unary operators

Q45. What type of scope does the end variable have in the code shown?

var start = 1;
if (start === 1) {
  let end = 2;
}

conditional
bloquear
global
função

Reference block vs function scope

Q46. What will the value of y be in this code:

const x = 6 % 2;
const y = x ? 'One' : 'Two';

1
indefinido
verdadeiro
Dois

Reference ternary operator js

Q47. Which keyword is used to create an error?

throw
exception
catch
error

Reference throwing errors in js

Q48. What’s one difference between the async and defer attributes of the HTML script tag?

The defer attribute can work synchronously.
The defer attribute works only with generators.
O atributo defer funciona apenas com promessas.
O atributo defer carregará os scripts de forma assíncrona em ordem.

Referência assíncrona vs adiada

Q49. O seguinte programa tem um problema. O que é isso?

var a;
var b = (a = 3) ? true : false;

A condição no ternário está usando o operador de atribuição.
Você não pode definir uma variável sem inicializá-la.
Você não pode usar um ternário no lado direito de um operador de atribuição.
O código está usando a palavra-chave var obsoleta.

Reference ternary operator js

Q50. Qual instrução faz referência ao nó DOM criado pelo código mostrado?

<p class="pull">lorem ipsum</p>

Document.querySelector('class.pull')
document.querySelector('.pull');
Document.querySelector('pull')
Document.querySelector('#pull')

Seletor de consulta de referência

Q51. Qual valor esse código retorna?

let answer = true;
if (answer === false) {
  return 0;
} else {
  return 10;
}

10
verdade
falso
0

Referência a condicionais javascript

Q52. Qual é o resultado no console da execução do código mostrado?

var start = 1;
function setEnd() {
  var end = 10;
}
setEnd();
console.log(end);

10
0
ReferenceError
indefinido

Referência

Q53. O que esse código registrará no console?

function sayHello() {
  console.log('hello');
}

console.log(sayHello.prototype);

indefinido
“olá”
um objeto com uma propriedade construtora
uma mensagem de erro

Protótipos de referência

Q54. Qual objeto de coleção permite que um valor único seja inserido apenas uma vez?

Objeto
Definir
Variedade
Mapa

Conjuntos javascript de referência

Q55. Quais são os dois valores que este código imprimirá?

function printA() {
  console.log(answer);
  var answer = 1;
}
printA();
printA();

1 então 1
1 então undefined
undefined então undefined
undefined então 1

Referência

Q56. Como é que `forEach()` method differ from a `for` declaração?

forEach allows you to specify your own iterator, whereas for does not.
forEach can be used only with strings, whereas for can be used with additional data types.
forEach can be used only with an array, whereas for can be used with additional data types.
for loops can be nested; whereas forEach loop cannot.

Diferenças de referência entre forEach e for loop

Q57. Which choice is an incorrect way to define an arrow function that returns an empty object?

=> ({})
=> {}
=> { return {};}
=> (({}))

Reference arrow functions

Q58. Why might you choose to make your code asynchronous?

to start tasks that might take some time without blocking subsequent tasks from executing immediately
to ensure that tasks further down in your code are not initiated until earlier tasks have completed
to make your code faster
to ensure that the call stack maintains a LIFO (Last in, First Out) estrutura

EXPLANATION: "to ensure that tasks further down in your code are not initiated until earlier tasks have completed" you use the normal (synchronous) flow where each command is executed sequentially. Asynchronous code allows you to break this sequence: start a long running function (AJAX call to an external service) and continue running the rest of the code in parallel.

Q59. Which expression evaluates to true?

[3] == [3]
3 == '3'
3 != '3'
3 === '3'

Q60. Which of these is a valid variable name?

5thItem
firstName
grand total
função

Reference coding conventions

Q61. Which method cancels event default behavior?

cancel()
stop()
preventDefault()
prevent()

Reference javascript events

Q62. Which method do you use to attach one DOM node to another?

attachNode()
getNode()
querySelector()
appendChild()

Reference Node interface

Q63. What statement can be used to skip an iteration in a loop?

break
pass
skip
continue

Reference break vs continue

Q64. Which choice is a valid example for an arrow function?

(a,b) => c
a, b => {return c;}
a, b => c
{ a, b } => c

Reference arrow functions

Q65. Which concept is defined as a template that can be used to generate different objects that share some shape and/or behavior?

classe
generator function
mapa
proxy

Classes javascript de referência

Q66. How do you add a comment to JavaScript code?

! This is a comment
# This is a comment
\\ This is a comment
// This is a comment

Reference comments in javascript

Q67. If you attempt to call a value as a function but the value is not a function, what kind of error would you get?

TypeError
SystemError
SyntaxError
LogicError

Reference javascript errors

Q68. Which method is called automatically when an object is initialized?

Criar()
Novo()
constructor()
init()

Reference javascript constructors

Q69. What is the result of running the statement shown?

let a = 5;
console.log(++a);

Reference ++x vs x++

Q70. You’ve written the event listener shown below for a form button, but each time you click the button, the page reloads. Which statement would stop this from happening?

button.addEventListener(
  'click',
  function (e) {
    button.className = 'clicked';
  },
  false,
);

e.blockReload();
button.preventDefault();
button.blockReload();
e.preventDefault();

Reference events in javascript

Q71. Which statement represents the starting code converted to an IIFE?

function() { console.log('lorem ipsum'); }()();
function() { console.log('lorem ipsum'); }();
(function() { console.log('lorem ipsum'); })();

Reference what is an Immediately Invoked Function Expression

Q72. Which statement selects all img elements in the DOM tree?

Document.querySelector('img')
Document.querySelectorAll('<img>')
Document.querySelectorAll('img')
Document.querySelector('<img>')

Seletor de consulta de referência

Q73. Why would you choose an asynchronous structure for your code?

To use ES6 syntax
To start tasks that might take some time without blocking subsequent tasks from executing immediately
To ensure that parsers enforce all JavaScript syntax rules when processing your code
To ensure that tasks further down in your code aren’t initiated until earlier tasks have completed

Reference async function

Q74. What is the HTTP verb to request the contents of an existing resource?

EXCLUIR
PEGAR
PATCH
PUBLICAR

Reference http methods

Q75. Which event is fired on a text field within a form when a user tabs to it, or clicks or touches it?

foco
blur
hover
entrar

Reference javascript events

Q76. Qual é o resultado no console da execução deste código?

function logThis() {
  console.log(this);
}
logThis();

função
indefinido
Function.prototype
janela

Reference what is the javascript window

Q77. Which class-based component is equivalent to this function component?

const Greeting = ({ name }) => <h1>Hello {name}!</h1>;

class Greeting extends React.Component { render() { return <h1>Hello {this.props.name}!</h1>; } }
class Greeting extends React.Component { constructor() { return <h1>Hello {this.props.name}!</h1>; } }
class Greeting extends React.Component { <h>Hello {this.props.name}!</h>; } }
class Greeting extends React.Component { render({ name }) { return <h1>Hello {name}!</h1>; } }

Q79. What is the output of this code?

var obj;
console.log(obj);

ReferenceError: obj is not defined
{}
undefined
null

Reference working with objects

Q80. How would you use the TaxCalculator to determine the amount of tax on $50?

class TaxCalculator {
  static calculate(total) {
    return total * 0.05;
  }
}

calcular(50);
new TaxCalculator().calcular($50);
TaxCalculator.calculate(50);
new TaxCalculator().calcular(50);

Funções de referência em javascript

Q81. What is wrong with this code?

const foo = {
  bar() {
    console.log('Hello, world!');
  },
  name: 'Albert',
  age: 26,
};

The function bar needs to be defined as a key/value pair.
Trailing commas are not allowed in JavaScript.
Functions cannot be declared as properties of objects.
Nenhuma coisa, there are no errors.

Q82. What will be logged to the console?

console.log('I');
setTimeout(() => {
  console.log('love');
}, 0);
console.log('Javascript!');

I
Javascript!
love

love
I
Javascript!

The output may change with each execution of code and cannot be determined.
.

I
love
Javascript!

Referência https://developer.mozilla.org/en-US/docs/Web/API/setTimeout#reasons_for_delays_longer_than_specified especially see the ‘late timeouts’ seção.

Q83. What will this code log to the console?

const foo = [1, 2, 3];
const [n] = foo;
console.log(n);

1
indefinido
NaN
Nenhuma coisa–this is not proper JavaScript syntax and will throw an error.

Reference array deconstruction

Q84. How do you remove the property name from this object?

const foo = {
  name: 'Albert',
};

delete name from foo;
delete foo.name;
del foo.name;
remove foo.name;

Reference working with objects

Q85. Qual é a diferença entre o `map()` e a `forEach()` methods on the Array prototype?

There is no difference.
o forEach() method returns a single output value, whereas the map() method performs operation on each value in the array.
The map() method returns a new array with a transformation applied on each item in the original array, whereas the forEach() method iterates through an array with no return value.
o forEach() method returns a new array with a transformation applied on each item in the original array, whereas the map() method iterates through an array with no return value.

Q86. Which concept does this code illustrate?

function makeAdder(x) {
  return function (y) {
    return x + y;
  };
}

var addFive = makeAdder(5);
console.log(addFive(3));

overloading
closure
currying
overriding

Reference currying

Q87. Which tag pair is used in HTML to embed JavaScript?

<script></script>
<js></js>
<javascript></javascript>
<code></code>

Reference add js to html file

Q88. If your app receives data from a third-party API, which HTTP response header must the server specify to allow exceptions to the same-origin policy?

Security-Mode
Access-Control-Allow-Origin
Different-Origin
Same-Origin

Reference Cross-Origin Resource Sharing

Q89. What is the output of this code?

let rainForests = ['Amazon', 'Borneo', 'Cerrado', 'Congo'];
rainForests.splice(0, 2);
console.log(rainForests);

["Amazon","Borneo","Cerrado","Congo"]
["Cerrado", "Congo"]
["Congo"]
["Amazon","Borneo"]

Reference array methods

Q90. Which missing line would allow you to create five variables(1,dois,três,quatro,five) that correspond to their numerical values (1,2,3,4,5)?

const numbers = [1, 2, 3, 4, 5];
//MISSING LINE

const [one,two,three,four,five]=numbers
const {one,two,three,four,five}=numbers
const [one,two,three,four,five]=[numbers]
const {one,two,three,four,five}={numbers}

Reference array destructuring

Q91. What will this code print?

const obj = {
  a: 1,
  b: 2,
  c: 3,
};

const obj2 = {
  ...obj,
  a: 0,
};

console.log(obj2.a, obj2.b);

Nenhuma coisa, it will throw an error
0 2
indefinido 2
indefinido 2

Reference spread syntax es6

Q92. Which line could you add to this code to print “jaguar” para a consola?

let animals = ['jaguar', 'eagle'];
//Missing Line
console.log(animals.pop()); //Prints jaguar

animals.filter(e => e === "jaguar");
animals.reverse();
animals.shift();
animals.pop();

Reference Javascript Array pop()

shift() – removes the FIRST element of an array and returns the removed item.

pop() – removes the LAST element of an array and returns the removed item.

reverse() – reverses the order of the elements in an array.

filtro() – get every element in the array that meets the condition.

Q93. What line is missing from this code?

//Missing Line
for (var i = 0; i < vowels.length; i++) {
  console.log(vowels[i]);
  //Each letter printed on a separate line as follows;
  //a
  //e
  //i
  //o
  //u
}

let vowels = "aeiou".toArray();
let vowels = Array.of("aeiou");
let vowels = {"a", "e", "i", "o", "u"};
let vowels = "aeiou";

Reference working with arrays

Q94. What will be logged to the console?

const x = 6 % 2;
const y = x ? 'One' : 'Two';
console.log(y);

indefinido
1
verdade
Dois

Nota: this question is same with Q46. Reference ternary operator js

Q95. How would you access the word It from this multidimensional array?

let matrix = [["You","Can"],["Do","It"],["!","!","!"]];

matrix[1[2]]
matrix[1][1]
matrix[1,2]
matrix[1][2]

Q96. What does this code do?

const animals = ['Rabbit', 'Dog', 'Cat'];
animals.unshift('Lizard');

It adds “Lizard” to the start of the animals array.
It adds “Lizard” to the end of the animals array.
It replaces “Rabbit” com “Lizard” in the animals array.
It replaces “Cat” com “Lizard” in the animals array.

Reference working with arrays

Q97. What is the output of this code?

let x = 6 + 3 + '3';
console.log(x);

Reference type coercion

Q98. Which statement can take a single expression as input and then look through a number of choices until one that matches that value is found?

senão
quando
E se
interruptor

Reference switch

Q99. Which statement prints “roar” para a consola?

var sound = 'grunt';
var bear = { sound: 'roar' };
function roar() {
  console.log(this.sound);
}

bear.bind(roar);
roar.bind(bear);
roar.apply(bear);
bear[roar]();

Q100. Which choice is a valid example of an arrow function, assuming c is defined in the outer scope?

a, b => { return c; }
a, b => c
{ a, b } => c
(a,b) => c

Reference arrow functions

Q101. Which statement correctly imports this code from some-file.js?

//some-file.js
export const printMe = (str) => console.log(str);

import printMe from './some-file';
import { printMe } from './some-file';
import default as printMe from './some-file';
const printMe = import './some-file';

Reference importing libraries in javascript

Q102. What will be the output of this code?

const arr1 = [2, 4, 6];
const arr2 = [3, 5, 7];

console.log([...arr1, ...arr2]);

Reference spread syntax

Q103. Which method call is chained to handle a successful response returned by `fetch()`?

done()
then()
finally()
catch()

Reference fetch

Q104. Which choice is not an array method?

array.slice()
array.shift()
array.push()
array.replace()

Reference working with arrays

Q105. Which JavaScript loop ensures that at least a singular iteration will happen?

do…while
forEach
enquanto
para

Reference loops in js

Q106. What will be logged to the console?

console.log(typeof 'blueberry');

string
array
Boolean
object

Reference what is typeof

Q107. What is the output that is printed when the div containing the text “Click Here” is clicked?

//HTML Markup
<div id="A">
  <div id="B">
    <div id="C">Click Here</div>
  </div>
</div>

//JavaScript
document.querySelectorAll('div').forEach((e) => {
  e.onclick = (e) => console.log(e.currentTarget.id);
});

C B A
UMA
C
A B C

Q108. What will this code log to the console?

const myNumbers = [1, 2, 3, 4, 5, 6, 7];
const myFunction = (arr) => {
  return arr.map((x) => x + 3).filter((x) => x < 7);
};
console.log(myFunction(myNumbers));

[4,5,6,7,8,9,10]
[4,5,6,7]
[1,2,3,4,5,6]
[4,5,6]

Funções de referência em javascript

Q109. What does this code print to the console?

let rainForestAcres = 10;
let animals = 0;

while (rainForestAcres < 13 || animals <= 2) {
  rainForestAcres++;
  animals += 2;
}

console.log(animals);

Reference MDN JavaScript Looping code

Q110. Qual trecho você poderia adicionar a este código para imprimir “YOU GOT THIS” para a consola?

let cipherText = [...'YZOGUT QGMORTZ MTRHTILS'];
let plainText = '';

/* Missing Snippet */

console.log(plainText); //Prints YOU GOT THIS

for (let key of cipherText.keys()) {
  plainText += key % 2 === 0 ? key : ' ';
}

for (let [index, value] of cipherText.entries()) {
  plainText += index % 2 !== 0 ? value : '';
}

for (let [index, value] of cipherText.entries()) {
  plainText += index % 2 === 0 ? value : '';
}

for (let value of cipherText) {
  plainText += value;
}

Q111. Which Pokemon will be logged to the console?

var pokedex = ['Snorlax', 'Jigglypuff', 'Charmander', 'Squirtle'];
pokedex.pop();
console.log(pokedex.pop());

Charmander
Jigglypuff
Snorlax
Squirtle

Explicação: The pop() method removes the last element from an array and returns that element. This method changes the length of the array.

Reference Array.pop

Q112. Which statement can be used to select the element from the DOM containing the text “The LinkedIn Learning library has great JavaScript courses” from this markup?

<h1 class="content">LinkedIn Learning</h1>
<div class="content">
  <span class="content">The LinkedIn Learning library has great JavaScript courses!</span>
</div>

document.querySelector(“div.content”)
document.querySelector(“span.content”)
document.querySelector(“.contente”)
document.querySelector(“div.span”)

Q113. Which value is not falsey?

[]
undefined
0
null

Reference Falsy

Q114. What line of code causes this code segment to throw an error?

const lion = 1;
let tiger = 2;
var bear;

++lion;
bear += lion + tiger;
tiger++;

line 5, because lion cannot be reassigned a value
line 6, because the += operator cannot be used with the undefined variable bear
line 5, because the prefix (++) operator does not exist in JavaScript
line 3, because the variable bear is left undefined

Q115. What will be the value of `result` after running this code?

const person = { name: 'Dave', age: 40, hairColor: 'blue' };
const result = Object.keys(person).map((x) => x.toUpperCase());

It will throw a TypeError.
["Name", "Age", "HairColor"]
["DAVE", 40, "BLUE"]
["NAME", "AGE", "HAIRCOLOR"]

Q116. Which snippet could you insert to this code to print “nadar” para a consola?

let animals = ["eagle", "osprey", "salmon"];
let key = animal => animal === "salmon";

if(/* Insert Snippet Here */){
  console.log("swim");
}

animals.every(key)
animals.some(key).length === 1
animals.filter(key) === true
animals.some(key)

Reference Array.prototype.some

Q117. What is the output of this code?

class RainForest {
  static minimumRainFall = 60;
}

let congo = new RainForest();
RainForest.minimumRainFall = 80;
console.log(congo.minimumRainFall);

undefined
None of these answers, as static is not a feature in Javascript.
60
80

Reference Classes static

Q118. How can you attempt to access the property `a.b` em `obj` without throwing an error if a is undefined?

let obj = {};

obj?.a.b
obj.a?.b
obj[a][b]
obj.?a.?b

Reference Optional chaining (?.)

Q119. What happens when you run this code?

if (true) {
  var x = 5;
  const y = 6;
  let z = 7;
}
console.log(x + y + z);

It will throw a ReferenceError sobre x.
It will print 18.
It will print undefined.
It will throw a ReferenceError sobre y.

Reference let statement

Q120. What does this code print to the console?

const x = [1, 2];
const y = [5, 7];
const z = [...x, ...y];
console.log(z);

[1,2,5,7]
[[1, 2], [5, 7]]
[2,7]
[2,1,7,5]

Reference spread syntax (…)

Q121. Given this code, which statement will be evaluated as false?

const a = { x: 1 };
const b = { x: 1 };

a['x'] === b['x']
a != b
a === b
a.x === b.x

Referência

Q122. What will this code log to the console?

console.log(typeof 41.1);

Nothing. It resuults in a ReferenceError.
decimal
float
number

Referência

Q123. What is the output of this code?

let scores = [];
scores.push(1, 2);
scores.pop();
scores.push(3, 4);
scores.pop();
score = scores.reduce((a, b) => a + b);
console.log(score);

Q124. What does this code print to the console?

let bear = {
  sound: 'roar',
  roar() {
    console.log(this.sound);
  },
};

bear.sound = 'grunt';
let bearSound = bear.roar;
bearSound();

Nothing is printed to the console.
grunt
undefined
roar

Referência

Q125. What is the output of this code?

var cat = { name: 'Athena' };

function swap(feline) {
  feline.name = 'Wild';
  feline = { name: 'Tabby' };
}

swap(cat);
console.log(cat.name);

indefinido
Wild
Tabby
Athena

Q126. What will this code output to the log?

var thing;
let func = (str = 'no arg') => {
  console.log(str);
};
func(thing);
func(null);

null no arg
no arg no arg
null null
no arg null

Q127. What will this code print to the console?

const myFunc = () => {
  const a = 2;
  return () => console.log('a is ' + a);
};
const a = 1;
const test = myFunc();
test();

a is 1
a is undefined
It won’t print anything.
a is 2

Q128. What will this code print to the console?

const myFunc = (num1, num2 = 2, num3 = 2) => {
  return num1 + num2 + num3;
};
let values = [1, 5];
const test = myFunc(2, ...values);
console.log(test);

Q129. Which code would you use to access the Irish flag?

var flagsJSON =
  '{ "countries" : [' +
  '{ "country":"Ireland" , "flag":"🇮🇪" },' +
  '{ "country":"Serbia" , "flag":"🇷🇸" },' +
  '{ "country":"Peru" , "flag":"🇵🇪" } ]}';

var flagDatabase = JSON.parse(flagsJSON);

flagDatabase.countries[1].flag
flagDatabase.countries[0].flag
flagDatabase[1].flag
flagsJSON.countries[0].flag

Q130. Which snippet allows the acresOfRainForest variable to increase?

let conservation = true;
let deforestation = false;
let acresOfRainForest = 100;
if (/* Snipped goes here */){
    ++acresOfRainForest;
}

conservação && !desmatamento
!desmatamento && !conservação
!conservação || desmatamento
desmatamento && conservação || desmatamento

Q131. Which of these evaluate to true?

Boolean(“falso”)
Boolean(“”)
Boolean(0)
Boolean(NaN)

Q132. How would you add a data item named animal with a value of sloth to local storage for the current domain?

LocalStorage.setItem(“animal”,”sloth”);
document.localStorage.setItem(“animal”,”sloth”);
localStorage.setItem({animal:”sloth”});
localStorage.setItem(“animal”,”sloth”);

Referência

Q133. What value is printed to the console after this code execute?

let cat = Object.create({ type: 'lion' });
cat.size = 'large';

let copyCat = { ...cat };
cat.type = 'tiger';

console.log(copyCat.type, copyCat.size);

tiger large
lion undefined
undefined large
lion large

Referência

Q134. What does this code print to the console?

let animals = [{ type: 'lion' }, 'tiger'];
let clones = animals.slice();

clones[0].type = 'bear';
clones[1] = 'sheep';

console.log(animals[0].type, clones[0].type);
console.log(animals[1], clones[1]);

bear bear tiger sheep
lion bear sheep sheep
bear bear tiger tiger
lion bear tiger sheep

Referência

Q135. What will be the output of the following code?

a=5;
b=4;
alert(a++(+(+(+b))));

Q136. Qual trecho você poderia adicionar a este código para imprimir “{“tipo”: “Tigre siberiano”}” para a consola?

let cat = { type: "tiger", size: "large" };

let json = /* Snippet here */;

console.log(json); // print {"type":"tiger"}

cat.toJSON("type");
JSON.stringify(cat, ["type"]);
JSON.stringify(cat);
JSON.stringify(cat, /type/);

Referência

Q137. Which document method is not used to get a reference to a DOM node?

document.getNode();
document.getElementsByClassName();
document.querySelectorAll();
document.querySelector();

Referência

Q138. In JavaScript, all objects inherit a built-in property from a ****___.

node
instance variable
prototype
accessor

Referência

Q139. Which of the following are not server-side Javascript objects?

Date
FileUpload
Função
Tudo acima

Referência

Q140. What will be the output of the following code snippet?

const obj1 = { first: 20, second: 30, first: 50 };
console.log(obj1);

primeiro: 30 , é importante entender por que esses animais passaram a ser parte integrante da identidade canadense: 50
primeiro: 50 , é importante entender por que esses animais passaram a ser parte integrante da identidade canadense: 30
primeiro: 30 , é importante entender por que esses animais passaram a ser parte integrante da identidade canadense: 20
Nenhuma das acima

Q141. Which object in Javascript doesn’t have a prototype?

Base Object
All objects have prototype
None of the objects have prototype
Nenhuma das acima

Referência

Q142. What does … operator do in JS?

Used to spread iterables to individual elements
Describe datatype of undefined
No such operator exists
Nenhuma das acima

Q143. How to stop an interval timer in Javascript?

clearInterval
clearTimer
intervalOver
Nenhuma das acima

Referência

Q144. What will be the output of the following code snippet?

print(typeof NaN);

Objeto
Number
Corda
Nenhuma das acima

Q145. What will be the output of the following code snippet?

<script type="text/javascript">a = 5 + "9"; document.write(a);</script>

Compilation Error
14
Runtime Error
59

Q146. Which of the following methods can be used to display data in some form using Javascript?

document.write()
console.log()
window.alert()
all of the above

Q147. What value is assigned to total after this code executes?

function sum(num1, num2 = 2, num3 = 3) {
  return num1 + num2 + num3;
}
let values = [1, 5];
let total = sum(4, ...values);

Referência: Rest parameters

Q148. Which statement is applicable to the defer attribute of the HTML <roteiro> tag?

defer allows the browser to continue processing the page while the script loads in the background.
defer causes the script to be loaded from the backup content delivery network (CDN).
defer blocks the browser from processing HTML below the tag until the script is completely loaded.
defer lazy loads the script, causing it to download only when it is called by another script on the page.

Referência: defer html script attribute

Q149. Which method of a class is called to initialize an object of that class?

init()
Criar()
Novo()
constructor()

Referência: constructor method

Q150. Which expression evaluates to true?

Boolean(NaN)
Boolean(0)
Boolean(“falso”)
Boolean(“”)

Referência: Boolean object

Q151. How would you check if the word “pot” is in the word “potato”?

“pot”.índice de(“potato”) !== -1
“potato”.includes(“Pot”)
“potato”.includes(“pot”)
“potato”.Associado engenheiro de segurança do Microsoft AZ-500 Azure(“pot”);

Referência: String.prototype.includes()

Q152. Which collection object allows a unique value to be inserted only once?

Mapa
Variedade
Definir
Objeto

Referência: developer.mozilla Set

Q153. How would you change the color of this header to pink?

<h2 id="cleverest">girls</h2>

document.getElementByName(“cleverest”).style.color = “cor de rosa”;
document.getElementsByTagName(“H2”).style.color = “cor de rosa”;
document.getElementByName(“H2”).style.color = “cor de rosa”;
document.getElementById(“cleverest”).style.color = “cor de rosa”;

Referência: W3Schools HTML DOM Style color Property

Q154. Which line is missing from this code if you expect the code to evaluate to true?

var compare = function (test1, test2) {
  // Missing line
};

compare(1078, '1078'); // yields true

test1==test2;
return test1===test2;
return test1==test2;
return test1!=test2;

Referência: MDN Equality Docs

Q155. What is the output of this code?

if (true) {
  var first = 'You';
}

function fScope() {
  var second = 'got this!';
}
fScope();
console.log(first);
console.log(second);

Você
indefinido
Você
ReferenceError
indefinido
indefinido
Você
got this!

Referência: W3schools JS Scoping

Q156. What is the output for the code given below?

console.log('hello' + 'world');

helloworld!
helloworld !
hello world!
hello world !

Q157. What is the output of this code?

console.log(10 + 10);

Q158. Events related to the browser window can be handled by?

Onclicks
Janela
querySelector
Nenhuma das acima

Referência: GeeksForGeeks

Q159. How do you define a function in JavaScript?

function myFunction() {}
def myFunction() {}
var myFunction = () => {}
func myFunction() {}

Referência

Q160. Your code is producing the error: TypeError: Cannot read property ‘reduce’ of undefined. O que isso significa?

You are calling a method named reduce on an object that’s declared but has no value.
You are calling a method named reduce on an object that does not exist.
You are calling a method named reduce on an empty array.
You are calling a method named reduce on an object that has a null value.

Q161. Which of the following methods can be used to display data in some form using Javascript?

document.write()
console.log()
window.alert()
all of the above

Q162. Which document method is not used to get a reference to a DOM node?

document.getNode();
document.getElementsByClassName();
document.querySelectorAll();
document.querySelector();

Q163. Which of these is a valid variable name?

5thItem
firstName
grand total
função

Q164. What function is used in JavaScript to schedule a function to run after a specified number of milliseconds?

setTimeout()
setInterval()
delay()
Eu incluí alguns exemplos concretos como recursos que você pode querer ler para um conhecimento mais aprofundado()

Referência

Q165. Which of the following is a server-side Java Script object?

Função
Arquivo
FileUpload
Date

Referência

Q166. Which statement best describes the var keyword’s scope in JavaScript?

Block scope
Function scope
Global scope
Instance scope

Q167. What will be logged to the console?

const foo = () => console.log('First');
const bar = () => setTimeout(() => console.log('Second'), 0);
foo();
bar();
console.log('Third');

Segundo, Primeiro, Terceiro
Primeiro, Terceiro, Segundo
Primeiro, Segundo, Terceiro
Terceiro, Primeiro, Segundo

Q168. What will be the output of running this code?

function scream(words) {
  return words.toUpperCase() + '!!!';
}

scream('yay');

YAY!!!
ReferenceError
Undefined
TypeError

Autor

Helen Bassey

Oi, Eu sou Helena, um redator de blog apaixonado por postar conteúdos interessantes no nicho educacional. Acredito que a educação é a chave para o desenvolvimento pessoal e social, e quero compartilhar meu conhecimento e experiência com alunos de todas as idades e origens. No meu blog, você encontrará artigos sobre tópicos como estratégias de aprendizagem, Educação online, orientação profissional, e mais. Também agradeço comentários e sugestões de meus leitores, então fique à vontade para deixar um comentário ou entrar em contato comigo a qualquer momento. Espero que você goste de ler meu blog e o considere útil e inspirador.
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