js数组去重的方式

方式一：new Set():返回一个对象

<script>
    var arr1 = [1,2,3,4,2,3,5,8,9];
    console.log(new Set(arr1);//{1,2,3,4,5,8,9}返回一个对象
    //转为真正的数组
    console.log(Array.from(new Set(arr1)));//[1,2,3,4,5,8,9]
    console.log([...new Set(arr1)])//[1,2,3,4,5,8,9]
    //封装为函数
    function unique(arr){
        return [...new Set(arr)]
    }
    console.log(unique(arr1));//[1,2,3,4,5,8,9]
</script>

方式二：indexOf

<script>
    var arr2 = [1,2,3,2,4,1]
    function unique(arr){
        var brr = [];
        for(var i=0;i<arr.length;i++){
            if(brr.indexOf(arr[i]) ==-1){
                brr.push(arr[i]);
            }
        }
        return brr;
    }
    console.log(unique(arr2));//[1,2,3,4]
</script>

方式三：sort排序后去重

<script>
    var arr3 = [1,2,3,2,4,1]
    function unique(arr){
        arr = arr.sort;
        var brr = [];
        for(var i=0;i<arr.length;i++){
            if(arr[i] !== arr[i-1]){
                brr.push(arr[i]);
            }
        }
        return brr;
    }
    console.log(unique(arr3));//[1,2,3,4]
</script>