Array.prototype.includes

Array.prototype.includes()

includes 返回true 如果数组中存在某个元素

let array = [1,2,4,5];

array.includes(2);
// true
array.includes(3);
// false

额外用法

includes 第二参数可以加入起始查找的索引（涵盖这个起始值）。默认情况下，是0。

let array = [1,3,5,7,9,11];

array.includes(3,1);
// find the number 3 starting from array index 1
// true
array.includes(5,4);
//false
array.includes(1,-1);
// find the number 1 starting from the ending of the array going backwards
// false
array.includes(11,-3);
// true