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二、ES7

20.includes

传入元素,如果数组中能找到此元素,则返回true,否则返回false

javascript
const includeArr = [1, 2 , 3, 'zk', '科比']

const isKobe = includeArr.includes('科比')
console.log(isKobe) // true

跟indexOf很像,但还是有区别的

javascript
const arr = [1, 2, NaN]

console.log(arr.indexOf(NaN)) // -1  indexOf找不到NaN
console.log(arr.includes(NaN)) // true includes能找到NaN

21.求迷运算符

以前求幂,我们需要这么写

javascript
const num = Math.pow(3, 2) // 9

ES7提供了求幂运算符:**

javascript
const num = 3 ** 2 // 9