JS-数组去重

数组去重的方法太多了，这里列举几个比较简单的

一、filter+indexOf

let res=[1,2,3,3,2,1]
let ad = res.filter((item, index, self) => {
  return self.indexOf(item) ===index
})
console.log(ad)
 
// [1,2,3]

// lastIndexOf和indexOf用法一样，只不过返回的数据的顺序和indexOf相反

二、for...of和indexOf/lastIndexOf/includes

let arr= [1,2,3,3,2,1]
 
let newc = []
 
for(let j of arr){
 
if(!newc.includes(j)) newc.push(j)
 
//if(newc.indexOf(j)===-1) newc.push(j)
 
//if(newc.lastIndexOf(j)===-1) newc.push(j)
 
}
 
console.log(newc)//[1,2,3]

三、new Set和展开运算符

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

四、new Set和Array.from

let arr =[1,2,3,3,2,1]
 
let res=Array.from(new Set(arr))
 
console.log(res)//[1,2,3]