// indexof 去重
var arr =[1,6,12,0,4,7,6,3];
function unique(arr){
    var arr1 = [];       
    // 新建一个数组来存放arr中的值
    for(var i=0,len=arr.length;i<len;i  ){
       if(arr1.indexOf(arr[i]) === -1){
       arr1.push(arr[i]);
    }
  }
  return arr1;
}
console.log(unique(arr)); // [1, 6, 12, 0, 4, 7, 3]
 
// set  去重
let arr = [212, 3, 25, 3, 6, 7, 25];
let item = [...new Set(arr)];
console.log(item); // [212, 3, 25, 6, 7]