数组相关题目

1.

const fruit = ['🍌', '🍊', '🍎']

fruit.slice(0, 1)
fruit.splice(0, 1)
fruit.unshift('🍇')

console.log(fruit)

A: ['🍌', '🍊', '🍎']
B: ['🍊', '🍎']
C: ['🍇', '🍊', '🍎']
D: ['🍇', '🍌', '🍊', '🍎']

答案： c slice不会改变原数组

2.

const groceries = ["banana", "apple", "peanuts"];

if (groceries.indexOf("banana")) {
 console.log("We have to buy bananas!");
} else {
 console.log(`We don't have to buy bananas!`);
}

• A: We have to buy bananas!
• B: We don't have to buy bananas
• C: undefined
• D: 1

答案： B

数组的indexof返回下标，返回的是0， false

3. 哪些方法修改了原数组?

const emojis = ['✨', '🥑', '😍']

emojis.map(x => x + '✨')
emojis.filter(x => x !== '🥑')
emojis.find(x => x !== '🥑')
emojis.reduce((acc, cur) => acc + '✨')
emojis.slice(1, 2, '✨')
emojis.splice(1, 2, '✨')

• A: All of them
• B: map reduce slice splice
• C: map slice splice
• D: splice

答案：D

splice是替换字符

4.

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

答案: D

push返回的是数组的新长度，此时newList的结果是4，而4是一个数字，不能使用数组的方法，所以报错。