1.indexOf()返回給定元素在數組內的索引值,如果不存在則返回-1
var arr=[0,1,2,3,4,5] console.log(arr.indexOf(1)) //1 console.log(arr.indexOf(1,2)) //-1 console.log(arr.indexOf(6)) //-1
2.ES6方法
let arr=[0,1,2,5,7,9] arr.includes(0) //true arr.includes(0,2) //false arr.includes(8) //false