JavaScript 进阶问题列表
我在我的 Instagram 上每天都会发布 JavaScript 的多选问题，并且同时也会在这个仓库中发布。
从基础到进阶，测试你有多了解 JavaScript，刷新你的知识，或者帮助你的 coding 面试！ 
我每周都会在这个仓库下更新新的问题。
答案在问题下方的折叠部分，点击即可展开问题。祝你好运 
1. 输出是什么？
function sayHi() {
console.log(name)
console.log(age)
var name = ‘Lydia‘
let age = 21
}
sayHi()
- A:
Lydia和undefined - B:
Lydia和ReferenceError - C:
ReferenceError和21 - D:
undefined和ReferenceError
2. 输出是什么？
for (var i = 0; i < 3; i++) {
setTimeout(() => console.log(i), 1)
}
for (let i = 0; i < 3; i++) {
setTimeout(() => console.log(i), 1)
}
- A:
0 1 2和0 1 2 - B:
0 1 2和3 3 3 - C:
3 3 3和0 1 2
3. 输出是什么？
const shape = {
radius: 10,
diameter() {
return this.radius * 2
},
perimeter: () => 2 * Math.PI * this.radius
}
shape.diameter()
shape.perimeter()
- A:
20and62.83185307179586 - B:
20andNaN - C:
20and63 - D:
NaNand63
4. 输出是什么？
+true;
!"Lydia";
- A:
1andfalse - B:
falseandNaN - C:
falseandfalse
5. 哪一个是无效的？
const bird = {
size: ‘small‘
}
const mouse = {
name: ‘Mickey‘,
small: true
}
- A:
mouse.bird.size - B:
mouse[bird.size] - C:
mouse[bird["size"]] - D: All of them are valid
6. 输出是什么？
let c = { greeting: ‘Hey!‘ }
let d
d = c
c.greeting = ‘Hello‘
console.log(d.greeting)
- A:
Hello - B:
undefined - C:
ReferenceError - D:
TypeError
7. 输出是什么？
let a = 3
let b = new Number(3)
let c = 3
console.log(a == b)
console.log(a === b)
console.log(b === c)
- A:
truefalsetrue - B:
falsefalsetrue - C:
truefalsefalse - D:
falsetruetrue
8. 输出是什么？
class Chameleon {
static colorChange(newColor) {
this.newColor = newColor
return this.newColor
}
constructor({ newColor = ‘green‘ } = {}) {
this.newColor = newColor
}
}
const freddie = new Chameleon({ newColor: ‘purple‘ })
freddie.colorChange(‘orange‘)
- A:
orange - B:
purple - C:
green - D:
TypeError
9. 输出是什么？
let greeting
greetign = {} // Typo!
console.log(greetign)
- A:
{} - B:
ReferenceError: greetign is not defined - C:
undefined
10. 当我们这么做时，会发生什么？
function bark() {
console.log(‘Woof!‘)
}
bark.animal = ‘dog‘
- A: 正常运行!
- B:
SyntaxError. 你不能通过这种方式给函数增加属性。 - C:
undefined - D:
ReferenceError
11. 输出是什么？
function Person(firstName, lastName) {
this.firstName = firstName;
this.lastName = lastName;
}
const member = new Person("Lydia", "Hallie");
Person.getFullName = function () {
return `${this.firstName} ${this.lastName}`;
}
console.log(member.getFullName());
- A:
TypeError - B:
SyntaxError - C:
Lydia Hallie - D:
undefinedundefined
12. 输出是什么？
function Person(firstName, lastName) {
this.firstName = firstName
this.lastName = lastName
}
const lydia = new Person(‘Lydia‘, ‘Hallie‘)
const sarah = Person(‘Sarah‘, ‘Smith‘)
console.log(lydia)
console.log(sarah)
- A:
Person {firstName: "Lydia", lastName: "Hallie"}andundefined - B:
Person {firstName: "Lydia", lastName: "Hallie"}andPerson {firstName: "Sarah", lastName: "Smith"} - C:
Person {firstName: "Lydia", lastName: "Hallie"}and{} - D:
Person {firstName: "Lydia", lastName: "Hallie"}andReferenceError
13. 事件传播的三个阶段是什么？
- A: Target > Capturing > Bubbling
- B: Bubbling > Target > Capturing
- C: Target > Bubbling > Capturing
- D: Capturing > Target > Bubbling
14. 所有对象都有原型。
- A: true
- B: false
15. 输出是什么？
function sum(a, b) {
return a + b
}
sum(1, ‘2‘)
- A:
NaN - B:
TypeError - C:
"12" - D:
3
16. 输出是什么？
let number = 0
console.log(number++)
console.log(++number)
console.log(number)
- A:
112 - B:
122 - C:
022 - D:
012
17. 输出是什么？
function getPersonInfo(one, two, three) {
console.log(one)
console.log(two)
console.log(three)
}
const person = ‘Lydia‘
const age = 21
getPersonInfo`${person} is ${age} years old`
- A:
"Lydia"21["", " is ", " years old"] - B:
["", " is ", " years old"]"Lydia"21 - C:
"Lydia"["", " is ", " years old"]21
18. 输出是什么？
function checkAge(data) {
if (data === { age: 18 }) {
console.log(‘You are an adult!‘)
} else if (data == { age: 18 }) {
console.log(‘You are still an adult.‘)
} else {
console.log(`Hmm.. You don‘t have an age I guess`)
}
}
checkAge({ age: 18 })
- A:
You are an adult! - B:
You are still an adult. - C:
Hmm.. You don‘t have an age I guess
19. 输出是什么？
function getAge(...args) {
console.log(typeof args)
}
getAge(21)
- A:
"number" - B:
"array" - C:
"object" - D:
"NaN"
20. 输出是什么？
function getAge() {
‘use strict‘
age = 21
console.log(age)
}
getAge()
- A:
21 - B:
undefined - C:
ReferenceError - D:
TypeError
21. 输出是什么？
const sum = eval(‘10*10+5‘)
- A:
105 - B:
"105" - C:
TypeError - D:
"10*10+5"
22. cool_secret 可访问多长时间？
sessionStorage.setItem(‘cool_secret‘, 123)
- A: 永远，数据不会丢失。
- B: 当用户关掉标签页时。
- C: 当用户关掉整个浏览器，而不只是关掉标签页。
- D: 当用户关闭电脑时。
23. 输出是什么？
var num = 8
var num = 10
console.log(num)
- A:
8 - B:
10 - C:
SyntaxError - D:
ReferenceError
24. 输出是什么？
const obj = { 1: ‘a‘, 2: ‘b‘, 3: ‘c‘ }
const set = new Set([1, 2, 3, 4, 5])
obj.hasOwnProperty(‘1‘)
obj.hasOwnProperty(1)
set.has(‘1‘)
set.has(1)
- A:
falsetruefalsetrue - B:
falsetruetruetrue - C:
truetruefalsetrue - D:
truetruetruetrue
25. 输出是什么？
const obj = { a: ‘one‘, b: ‘two‘, a: ‘three‘ }
console.log(obj)
- A:
{ a: "one", b: "two" } - B:
{ b: "two", a: "three" } - C:
{ a: "three", b: "two" } - D:
SyntaxError
26. JavaScript 全局执行上下文为你做了两件事：全局对象和 this 关键字。
- A: true
- B: false
- C: it depends
27. 输出是什么？
for (let i = 1; i < 5; i++) {
if (i === 3) continue
console.log(i)
}
- A:
12 - B:
123 - C:
124 - D:
134
28. 输出是什么？
String.prototype.giveLydiaPizza = () => {
return ‘Just give Lydia pizza already!‘
}
const name = ‘Lydia‘
name.giveLydiaPizza()
- A:
"Just give Lydia pizza already!" - B:
TypeError: not a function - C:
SyntaxError - D:
undefined
29. 输出是什么？
const a = {}
const b = { key: ‘b‘ }
const c = { key: ‘c‘ }
a[b] = 123
a[c] = 456
console.log(a[b])
- A:
123 - B:
456 - C:
undefined - D:
ReferenceError
30. 输出是什么？
const foo = () => console.log(‘First‘)
const bar = () => setTimeout(() => console.log(‘Second‘))
const baz = () => console.log(‘Third‘)
bar()
foo()
baz()
- A:
FirstSecondThird - B:
FirstThirdSecond - C:
SecondFirstThird - D:
SecondThirdFirst
31. 当点击按钮时，event.target是什么？
<div onclick="console.log(‘first div‘)">
<div onclick="console.log(‘second div‘)">
<button onclick="console.log(‘button‘)">
Click!
</button>
</div>
</div>
- A: Outer
div - B: Inner
div - C:
button - D: 一个包含所有嵌套元素的数组。
32. 当您单击该段落时，日志输出是什么？
<div onclick="console.log(‘div‘)">
<p onclick="console.log(‘p‘)">
Click here!
</p>
</div>
- A:
pdiv - B:
divp - C:
p - D:
div
33. 输出是什么？
const person = { name: ‘Lydia‘ }
function sayHi(age) {
console.log(`${this.name} is ${age}`)
}
sayHi.call(person, 21)
sayHi.bind(person, 21)
- A:
undefined is 21Lydia is 21 - B:
functionfunction - C:
Lydia is 21Lydia is 21 - D:
Lydia is 21function
34. 输出是什么？
function sayHi() {
return (() => 0)()
}
typeof sayHi()
- A:
"object" - B:
"number" - C:
"function" - D:
"undefined"
35. 下面哪些值是 falsy?
0
new Number(0)
(‘‘)
(‘ ‘)
new Boolean(false)
undefined
- A:
0,‘‘,undefined - B:
0,new Number(0),‘‘,new Boolean(false),undefined - C:
0,‘‘,new Boolean(false),undefined - D: All of them are falsy
36. 输出是什么？
console.log(typeof typeof 1)
- A:
"number" - B:
"string" - C:
"object" - D:
"undefined"
37. 输出是什么？
const numbers = [1, 2, 3]
numbers[10] = 11
console.log(numbers)
- A:
[1, 2, 3, 7 x null, 11] - B:
[1, 2, 3, 11] - C:
[1, 2, 3, 7 x empty, 11] - D:
SyntaxError
38. 输出是什么？
(() => {
let x, y
try {
throw new Error()
} catch (x) {
(x = 1), (y = 2)
console.log(x)
}
console.log(x)
console.log(y)
})()
- A:
1undefined2 - B:
undefinedundefinedundefined - C:
112 - D:
1undefinedundefined
39. JavaScript 中的一切都是？
- A: 基本类型与对象
- B: 函数与对象
- C: 只有对象
- D: 数字与对象
40. 输出是什么？
[[0, 1], [2, 3]].reduce(
(acc, cur) => {
return acc.concat(cur)
},
[1, 2]
)
- A:
[0, 1, 2, 3, 1, 2] - B:
[6, 1, 2] - C:
[1, 2, 0, 1, 2, 3] - D:
[1, 2, 6]
41. 输出是什么？
!!null
!!‘‘
!!1
- A:
falsetruefalse - B:
falsefalsetrue - C:
falsetruetrue - D:
truetruefalse
42. setInterval 方法的返回值是什么？
setInterval(() => console.log(‘Hi‘), 1000)
- A: 一个唯一的id
- B: 该方法指定的毫秒数
- C: 传递的函数
- D:
undefined
43. 输出是什么？
[...‘Lydia‘]
- A:
["L", "y", "d", "i", "a"] - B:
["Lydia"] - C:
[[], "Lydia"] - D:
[["L", "y", "d", "i", "a"]]
44. 输出是什么?
function* generator(i) {
yield i;
yield i * 2;
}
const gen = generator(10);
console.log(gen.next().value);
console.log(gen.next().value);
- A:
[0, 10], [10, 20] - B:
20, 20 - C:
10, 20 - D:
0, 10 and 10, 20
45. 返回值是什么?
const firstPromise = new Promise((res, rej) => {
setTimeout(res, 500, "one");
});
const secondPromise = new Promise((res, rej) => {
setTimeout(res, 100, "two");
});
Promise.race([firstPromise, secondPromise]).then(res => console.log(res));
- A:
"one" - B:
"two" - C:
"two" "one" - D:
"one" "two"
46. 输出是什么?
let person = { name: "Lydia" };
const members = [person];
person = null;
console.log(members);
- A:
null - B:
[null] - C:
[{}] - D:
[{ name: "Lydia" }]
47. 输出是什么?
const person = {
name: "Lydia",
age: 21
};
for (const item in person) {
console.log(item);
}
- A:
{ name: "Lydia" }, { age: 21 } - B:
"name", "age" - C:
"Lydia", 21 - D:
["name", "Lydia"], ["age", 21]
48. 输出是什么?
console.log(3 + 4 + "5");
- A:
"345" - B:
"75" - C:
12 - D:
"12"
49. num的值是什么?
const num = parseInt("7*6", 10);
- A:
42 - B:
"42" - C:
7 - D:
NaN
50. 输出是什么?
[1, 2, 3].map(num => {
if (typeof num === "number") return;
return num * 2;
});
- A:
[] - B:
[null, null, null] - C:
[undefined, undefined, undefined] - D:
[ 3 x empty ]
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:
12and33and64 - B:
12and23and34 - C:
1undefinedand2undefinedand3undefinedand4undefined - D:
12andundefined3andundefined4
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;
}
};
- A: 1
- B: 2
- C: 3
- D: 4
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").valueandgame.next().value - B:
game.next.value("Yes")andgame.next.value() - C:
game.next().valueandgame.next("Yes").value - D:
game.next.value()andgame.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;
}
- A: Yes
- B: No
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! 20Calculated! 20Calculated! 20 - B:
Calculated! 20From cache! 20Calculated! 20 - C:
Calculated! 20From cache! 20From cache! 20 - D:
Calculated! 20From cache! 20Error
79. 输出什么?
const myLifeSummedUp = ["?", "??", "??", "??"]
for (let item in myLifeSummedUp) {
console.log(item)
}
for (let item of myLifeSummedUp) {
console.log(item)
}
- A:
0123and"?""??""??""??" - B:
"?""??""??""??"and"?""??""??""??" - C:
"?""??""??""??"and0123 - D:
0123and{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:
nameLydiaandage21 - B:
["name", "Lydia"]and["age", 21] - C:
["name", "age"]andundefined - 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,6andb is bigger,3 - B:
a is bigger,undefinedandb is bigger,undefined - C:
undefinedandundefined - 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]]andundefined - B:
[1, [2, 3, 4]]and{ name: "Lydia", age: 21 } - C:
[1, 2, 3, 4]and{ name: "Lydia", age: 21 } - D:
Errorand{ 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
101.输出什么?
const one = (false || {} || null)
const two = (null || false || "")
const three = ([] || 0 || true)
console.log(one, two, three)
- A:
falsenull[] - B:
null""true - C:
{}""[] - D:
nullnulltrue
