Array.prototype.includes():
includes()作用,是查找一个值在不在 数组里,若是存在则返回true,不存在返回false
['a', 'b', 'c'].includes('a') // true
['a', 'b', 'c'].includes('d') // false
['a', 'b', 'c', 'd'].includes('b') // true
['a', 'b', 'c', 'd'].includes('b', 1) // true
['a', 'b', 'c', 'd'].includes('b', 2) // false
['a', 'b', 'c'].includes('a') //true
['a', 'b', 'c'].indexOf('a') > -1 //true
var arr = [1, 2, 3]
var a = 1;
arr.includes(a) //true
arr.indexOf(a) //0
[1, +0, 3, 4].includes(-0) //true
[1, +0, 3, 4].indexOf(-0) //1
var arr = [1, [2, 3], 4]
arr.includes([2, 3]) //false
arr.indexOf([2, 3]) //-1
let demo = [1, NaN, 2, 3]
demo.indexOf(NaN) //-1
demo.includes(NaN) //true