Javascript⼩⽩经典题型（⼆）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";
resolve a doi name
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;
}
};
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 " 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: ("Yes").value ().value
B: value("Yes") value()
C: ().value ("Yes").value
D: value() 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 solve("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;
}