51. 输出的是什么?
function getInfo(member, year) {
member.name = "Lydia";
year = "1998";
}
const person = { name: "Sarah" };
const birthYear = "1997";
getInfo(person, birthYear);
console.log(person, birthYear);
- A: { name: "Lydia" }, "1997"
- B: { name: "Sarah" }, "1998"
- C: { name: "Lydia" }, "1998"
- D: { name: "Sarah" }, "1997"
52. 输出是什么?
function greeting() {
throw "Hello world!";
}
function sayHi() {
try {
const data = greeting();
console.log("It worked!", data);
} catch (e) {
console.log("Oh no an error!", e);
}
}
sayHi();
- A: "It worked! Hello world!"
- B: "Oh no an error: undefined
- C: SyntaxError: can only throw Error objects
- D: "Oh no an error: Hello world!
53. 输出是什么?
function Car() {
this.make = "Lamborghini";
return { make: "Maserati" };
}
const myCar = new Car();
console.log(myCar.make);
- A: "Lamborghini"
- B: "Maserati"
- C: ReferenceError
- D: TypeError
54. 输出是什么?
(() => {
let x = (y = 10);
})();
console.log(typeof x);
console.log(typeof y);
- A: "undefined", "number"
- B: "number", "number"
- C: "object", "number"
- D: "number", "undefined"
55. 输出是什么?
class Dog {
constructor(name) {
this.name = name;
}
}
Dog.prototype.bark = function() {
console.log(`Woof I am ${this.name}`);
};
const pet = new Dog("Mara");
pet.bark();
delete Dog.prototype.bark;
pet.bark();
- A: "Woof I am Mara", TypeError
- B: "Woof I am Mara","Woof I am Mara"
- C: "Woof I am Mara", undefined
- D: TypeError, TypeError
56. 输出是什么?
const set = new Set([1, 1, 2, 3, 4]);
console.log(set);
A: [1, 1, 2, 3, 4]
B: [1, 2, 3, 4]
C: {1, 1, 2, 3, 4}
D: {1, 2, 3, 4}
57. 输出是什么?
// counter.js
let counter = 10;
export default counter;
// index.js
import myCounter from "./counter";
myCounter += 1;
console.log(myCounter);
- A: 10
- B: 11
- C: Error
- D: NaN
58. 输出是什么?
const name = "Lydia";
age = 21;
console.log(delete name);
console.log(delete age);
- A: false, true
- B: "Lydia", 21
- C: true, true
- D: undefined, undefined
59. 输出是什么?
const numbers = [1, 2, 3, 4, 5];
const [y] = numbers;
console.log(y);
- A: [[1, 2, 3, 4, 5]]
- B: [1, 2, 3, 4, 5]
- C: 1
- D: [1]
60. 输出是什么?
const user = { name: "Lydia", age: 21 };
const admin = { admin: true, ...user };
console.log(admin);
- A: { admin: true, user: { name: "Lydia", age: 21 } }
- B: { admin: true, name: "Lydia", age: 21 }
- C: { admin: true, user: ["Lydia", 21] }
- D: { admin: true }
61. 输出是什么?
const person = { name: "Lydia" };
Object.defineProperty(person, "age", { value: 21 });
console.log(person);
console.log(Object.keys(person));
- A: { name: "Lydia", age: 21 }, ["name", "age"]
- B: { name: "Lydia", age: 21 }, ["name"]
- C: { name: "Lydia"}, ["name", "age"]
- D: { name: "Lydia"}, ["age"]
62. 输出是什么?
const settings = {
username: "lydiahallie",
level: 19,
health: 90
};
const data = JSON.stringify(settings, ["level", "health"]);
console.log(data);
- A: "{"level":19, "health":90}"
- B: "{"username": "lydiahallie"}"
- C: "["level", "health"]"
- D: "{"username": "lydiahallie", "level":19, "health":90}"
63. 输出是什么?
let num = 10;
const increaseNumber = () => num++;
const increasePassedNumber = number => number++;
const num1 = increaseNumber();
const num2 = increasePassedNumber(num1);
console.log(num1);
console.log(num2);
- A: 10, 10
- B: 10, 11
- C: 11, 11
- D: 11, 12
64. 输出什么?
const value = { number: 10 };
const multiply = (x = { ...value }) => {
console.log(x.number *= 2);
};
multiply();
multiply();
multiply(value);
multiply(value);
- A: 20, 40, 80, 160
- B: 20, 40, 20, 40
- C: 20, 20, 20, 40
- D: NaN, NaN, 20, 40
65. 输出什么?
[1, 2, 3, 4].reduce((x, y) => console.log(x, y));
- A: 1 2 and 3 3 and 6 4
- B: 1 2 and 2 3 and 3 4
- C: 1 undefined and 2 undefined and 3 undefined and 4 undefined
- D: 1 2 and undefined 3 and undefined 4
66. 使用哪个构造函数可以成功继承Dog类?
class Dog {
constructor(name) {
this.name = name;
}
};
class Labrador extends Dog {
// 1
constructor(name, size) {
this.size = size;
}
// 2
constructor(name, size) {
super(name);
this.size = size;
}
// 3
constructor(size) {
super(name);
this.size = size;
}
// 4
constructor(name, size) {
this.name = name;
this.size = size;
}
};
67. 输出什么?
// index.js
console.log('running index.js');
import { sum } from './sum.js';
console.log(sum(1, 2));
// sum.js
console.log('running sum.js');
export const sum = (a, b) => a + b;
- A: running index.js, running sum.js, 3
- B: running sum.js, running index.js, 3
- C: running sum.js, 3, running index.js
- D: running index.js, undefined, running sum.js
68. 输出什么?
console.log(Number(2) === Number(2))
console.log(Boolean(false) === Boolean(false))
console.log(Symbol('foo') === Symbol('foo'))
- A: true, true, false
- B: false, true, false
- C: true, false, true
- D: true, true, true
69. 输出什么?
const name = "Lydia Hallie"
console.log(name.padStart(13))
console.log(name.padStart(2))
- A: "Lydia Hallie", "Lydia Hallie"
- B: " Lydia Hallie", " Lydia Hallie" ("[13x whitespace]Lydia Hallie", "[2x whitespace]Lydia Hallie")
- C: " Lydia Hallie", "Lydia Hallie" ("[1x whitespace]Lydia Hallie", "Lydia Hallie")
- D: "Lydia Hallie", "Lyd"
70. 输出什么?
console.log("??" + "??");
- A: "????"
- B: 257548
- C: A string containing their code points
- D: Error
71. 如何能打印出console.log语句后注释掉的值?
function* startGame() {
const answer = yield "Do you love JavaScript?";
if (answer !== "Yes") {
return "Oh wow... Guess we're gone here";
}
return "JavaScript loves you back ??";
}
const game = startGame();
console.log(/* 1 */); // Do you love JavaScript?
console.log(/* 2 */); // JavaScript loves you back ??
- A: game.next("Yes").value and game.next().value
- B: game.next.value("Yes") and game.next.value()
- C: game.next().value and game.next("Yes").value
- D: game.next.value() and game.next.value("Yes")
72. 输出什么?
console.log(String.raw`Hello\nworld`);
- A: Hello world!
- B: Hello
- world
- C: Hello\nworld
- D: Hello\n
- world
73. 输出什么?
async function getData() {
return await Promise.resolve("I made it!");
}
const data = getData();
console.log(data);
- A: "I made it!"
- B: Promise {<resolved>: "I made it!"}
- C: Promise {<pending>}
- D: undefined
74. 输出什么?
function addToList(item, list) {
return list.push(item);
}
const result = addToList("apple", ["banana"]);
console.log(result);
- A: ['apple', 'banana']
- B: 2
- C: true
- D: undefined
75. 输出什么?
const box = { x: 10, y: 20 };
Object.freeze(box);
const shape = box;
shape.x = 100;
console.log(shape)
- A: { x: 100, y: 20 }
- B: { x: 10, y: 20 }
- C: { x: 100 }
- D: ReferenceError
76. 输出什么?
const { name: myName } = { name: "Lydia" };
console.log(name);
- A: "Lydia"
- B: "myName"
- C: undefined
- D: ReferenceError
77. 以下是个纯函数么?
function sum(a, b) {
return a + b;
}
78. 输出什么?
const add = () => {
const cache = {};
return num => {
if (num in cache) {
return `From cache! ${cache[num]}`;
} else {
const result = num + 10;
cache[num] = result;
return `Calculated! ${result}`;
}
};
};
const addFunction = add();
console.log(addFunction(10));
console.log(addFunction(10));
console.log(addFunction(5 * 2));
- A: Calculated! 20 Calculated! 20 Calculated! 20
- B: Calculated! 20 From cache! 20 Calculated! 20
- C: Calculated! 20 From cache! 20 From cache! 20
- D: Calculated! 20 From cache! 20 Error
79. 输出什么?
const myLifeSummedUp = ["?", "??", "??", "??"]
for (let item in myLifeSummedUp) {
console.log(item)
}
for (let item of myLifeSummedUp) {
console.log(item)
}
- A: 0 1 2 3 and "?" "??" "??" "??"
- B: "?" "??" "??" "??" and "?" "??" "??" "??"
- C: "?" "??" "??" "??" and 0 1 2 3
- D: 0 1 2 3 and {0: "?", 1: "??", 2: "??", 3: "??"}
80. 输出什么?
const list = [1 + 2, 1 * 2, 1 / 2]
console.log(list)
- A: ["1 + 2", "1 * 2", "1 / 2"]
- B: ["12", 2, 0.5]
- C: [3, 2, 0.5]
- D: [1, 1, 1]
81. 输出什么?
function sayHi(name) {
return `Hi there, ${name}`
}
console.log(sayHi())
- A: Hi there,
- B: Hi there, undefined
- C: Hi there, null
- D: ReferenceError
82. 输出什么?
var status = "??"
setTimeout(() => {
const status = "??"
const data = {
status: "??",
getStatus() {
return this.status
}
}
console.log(data.getStatus())
console.log(data.getStatus.call(this))
}, 0)
- A: "??" and "??"
- B: "??" and "??"
- C: "??" and "??"
- D: "??" and "??"
83. 输出什么?
const person = {
name: "Lydia",
age: 21
}
let city = person.city
city = "Amsterdam"
console.log(person)
- A: { name: "Lydia", age: 21 }
- B: { name: "Lydia", age: 21, city: "Amsterdam" }
- C: { name: "Lydia", age: 21, city: undefined }
- D: "Amsterdam"
84. 输出什么?
function checkAge(age) {
if (age < 18) {
const message = "Sorry, you're too young."
} else {
const message = "Yay! You're old enough!"
}
return message
}
console.log(checkAge(21))
- A: "Sorry, you're too young."
- B: "Yay! You're old enough!"
- C: ReferenceError
- D: undefined
85. 什么样的信息将被打印?
fetch('https://www.website.com/api/user/1')
.then(res => res.json())
.then(res => console.log(res))
- A: fetch方法的结果
- B: 第二次调用fetch方法的结果
- C: 前一个.then()中回调方法返回的结果
- D: 总是undefined
86. 哪个选项是将hasName设置为true的方法,前提是不能将true作为参数传递?
function getName(name) {
const hasName = //
}
- A: !!name
- B: name
- C: new Boolean(name)
- D: name.length
87. 输出什么?
console.log("I want pizza"[0])
- A: """
- B: "I"
- C: SyntaxError
- D: undefined
88. 输出什么?
function sum(num1, num2 = num1) {
console.log(num1 + num2)
}
sum(10)
- A: NaN
- B: 20
- C: ReferenceError
- D: undefined
89. 输出什么?
// module.js
export default () => "Hello world"
export const name = "Lydia"
// index.js
import * as data from "./module"
console.log(data)
- A: { default: function default(), name: "Lydia" }
- B: { default: function default() }
- C: { default: "Hello world", name: "Lydia" }
- D: Global object of module.js
90. 输出什么?
class Person {
constructor(name) {
this.name = name
}
}
const member = new Person("John")
console.log(typeof member)
- A: "class"
- B: "function"
- C: "object"
- D: "string"
91. 输出什么?
let newList = [1, 2, 3].push(4)
console.log(newList.push(5))
- A: [1, 2, 3, 4, 5]
- B: [1, 2, 3, 5]
- C: [1, 2, 3, 4]
- D: Error
92. 输出什么?
function giveLydiaPizza() {
return "Here is pizza!"
}
const giveLydiaChocolate = () => "Here's chocolate... now go hit the gym already."
console.log(giveLydiaPizza.prototype)
console.log(giveLydiaChocolate.prototype)
- A: { constructor: ...} { constructor: ...}
- B: {} { constructor: ...}
- C: { constructor: ...} {}
- D: { constructor: ...} undefined
93. 输出什么?
const person = {
name: "Lydia",
age: 21
}
for (const [x, y] of Object.entries(person)) {
console.log(x, y)
}
- A: name Lydia and age 21
- B: ["name", "Lydia"] and ["age", 21]
- C: ["name", "age"] and undefined
- D: Error
94. 输出什么?
function getItems(fruitList, ...args, favoriteFruit) {
return [...fruitList, ...args, favoriteFruit]
}
getItems(["banana", "apple"], "pear", "orange")
- A: ["banana", "apple", "pear", "orange"]
- B: [["banana", "apple"], "pear", "orange"]
- C: ["banana", "apple", ["pear"], "orange"]
- D: SyntaxError
95. 输出什么?
function nums(a, b) {
if
(a > b)
console.log('a is bigger')
else
console.log('b is bigger')
return
a + b
}
console.log(nums(4, 2))
console.log(nums(1, 2))
- A: a is bigger, 6 and b is bigger, 3
- B: a is bigger, undefined and b is bigger, undefined
- C: undefined and undefined
- D: SyntaxError
96. 输出什么?
class Person {
constructor() {
this.name = "Lydia"
}
}
Person = class AnotherPerson {
constructor() {
this.name = "Sarah"
}
}
const member = new Person()
console.log(member.name)
- A: "Lydia"
- B: "Sarah"
- C: Error: cannot redeclare Person
- D: SyntaxError
97. 输出什么?
const info = {
[Symbol('a')]: 'b'
}
console.log(info)
console.log(Object.keys(info))
- A: {Symbol('a'): 'b'} and ["{Symbol('a')"]
- B: {} and []
- C: { a: "b" } and ["a"]
- D: {Symbol('a'): 'b'} and []
98. 输出什么?
const getList = ([x, ...y]) => [x, y]
const getUser = user => { name: user.name, age: user.age }
const list = [1, 2, 3, 4]
const user = { name: "Lydia", age: 21 }
console.log(getList(list))
console.log(getUser(user))
- A: [1, [2, 3, 4]] and undefined
- B: [1, [2, 3, 4]] and { name: "Lydia", age: 21 }
- C: [1, 2, 3, 4] and { name: "Lydia", age: 21 }
- D: Error and { name: "Lydia", age: 21 }
99. 输出什么?
const name = "Lydia"
console.log(name())
- A: SyntaxError
- B: ReferenceError
- C: TypeError
- D: undefined
100. 输出什么?
// ??? This is my 100th question! ???
const output = `${[] && 'Im'}possible!
You should${'' && `n't`} see a therapist after so much JavaScript lol`
- A: possible! You should see a therapist after so much JavaScript lol
- B: Impossible! You should see a therapist after so much JavaScript lol
- C: possible! You shouldn't see a therapist after so much JavaScript lol
- D: Impossible! You shouldn't see a therapist after so much JavaScript lol