数组去重

1. ES6 的 Set函数       

let arr = [1,2,3,4,1,2,3];
let arr2 = [...new Set(arr)];
console.log(arr2 ) //1,2,3,4

2.filter过滤   

let arr = [0,2,3,4,4,0,2];
let arr2 = arr.filter((item,index,self)=>{
   return self.indexOf(item) === index
})
console.log(arr2)//0,2,3,4

 3.对象键值对

let arr =[1,2,3,4,1,2,3];
let obj = {};
let arr2 = [];
for(let value of arr){
   if(!obj[value]){
       obj[value] = 1;
       arr2.push(value)
   }
}
console.log(arr2)//1,2,3,4

4.indexOf

let arr = [1,2,3,4,1,4];
let arr2 = [];
for(let value of arr){
    if(arr2.indexOf(value)<0){
       arr2.push(value ) 
    }
}
console.log(arr2 )//1,2,3,4