JS数组索引方法

var arr = ['a','b','c','b']
console.log(arr.indexOf('b'))//返回1
console.log(arr.indexOf('d'))//返回-1

var arr = ['a','b','c','b']
    console.log(arr.indexOf('b'))//返回1
    console.log(arr.lastIndexOf('b'))//返回3

//去掉arr的重复元素
var arr = ['a','b','c','b','a'];

var arr = ['a','b','c','b','a'];
    var newArr = [];
    for(var i=0;i<arr.length;i++){
        if(newArr.indexOf(arr[i])==-1){
            newArr.push(arr[i])
        }
    }
    console.log(newArr)//['a','b','c']