JS去重的几种方法

//1、set方法去重，Array.from转化为数组

var a=[1,2,3,3,2,1,4,4]

var b = new Set(a)

b = Array.from(b)

console.log('b',b)

//2、set方法去重，展开元素赋值[...arr]

var a = [2,4,4,5,5,3,33,3,3,3]

var b = new Set(a)

b= [...b]

console.log('b',b)

//3、双重for循环

var a = [1,2,1,2,4,5,6,3,3,5]

var res = unique(a)

function unique(a) {

for(var i=0;i<a.length;i++){

 for(var j=i+1;j<a.length;j++){

  if(a[i] == a[j]){

   a.splice(j,1)

   j--

  }

 }

}

return a

}

console.log(res)

// 4、利用indexOf去重 + for循环

var array = []

for(var i = 0;i<arr.length;i++) {

if(array.indexOf(arr[i])=== -1){

 array.push(arr[i])

}

}

console.log('res',array)

5、利用filter()去重 + indexOf

var arr = [3,3,44,21,22,21,12]

var newArr = arr.filter((item,index)=>{

return arr.indexOf(item) === index  //因为indexOf 只能查找到第一个

})

console.log('newArr',newArr)

6、利用sort去重

var arr = [2,2,3,2,3,4,5,6,5]

arr.sort = arr.sort()

var a = [arr[0]]

for(var i= 1;i<arr.length;i++){

if(arr[i]!==arr[i-1]){

 a.push(arr[i])

}

}

console.log('a',a)

//7、利用includes实现数组去重

var arr= [1,1,22,2,23,33,333,223,2311,1,2,2,22,2]

var newArr = []

for(var i=0;i<arr.length;i++){

if(!newArr.includes(arr[i])){

 newArr.push(arr[i])

}

}

console.log(newArr)