indexOf

获取数组中某个指定的元素位置。

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var a = fruits.indexOf("Apple");
输出2

常用来判断是否在数组中

var fruits = ["Banana", "Orange", "Apple", "Mango"];
if(fruits .indexOf("Banana") !== -1){
  console.log("在数组里")
}