js数组去重

1.reduce 结合 includes

let array = [1,2,3,4,21,2,333,12,33,44,55,1,2,3,4,5]     

   let arry2 = array.reduce(function(pre,cut){         

   if(!pre.includes(cut)){     

           pre.push(cut)        

    }         

   return pre    

    },[])       

 conso0le.log(arry2)

2.for循环splice 删除重复元素

let array = [1,2,3,4,21,2,333,12,33,44,55,1,2,3,4,5]      

  for(let i=0;i

       for(let j = i+1;j

            if(array[i] == array[j]){           

                 array.splice(j,1)                

                    j--          

                  }         

           }      

          }    

    console.log(array) 

3. forEach  结合 includes indexOf

 let array = [1,2,3,4,21,2,333,12,33,44,55,1,2,3,4,5]      

 let newArr = []      

  array.forEach(function(cut,index)    {    

        // if(newArr.indexOf(cut)==-1) {          

         //     newArr.push(cut)         

       // }        

        //同理可以用 includes             

      if(!newArr.includes(cut)) {       

         newArr.push(cut) 

           }      

  })     

   console.log(newArr) 

4. filter 结合indexOf

let array = [1,2,3,4,21,2,333,12,33,44,55,1,2,3,4,5]    

    let array2 = array.filter(function(item,index)    {       

     return array.indexOf(item) === index    

    })         

console.log(array2) 

5.ES6  set 

Array,from(new Set(arr))

或者简化为[...new Set(arr)] 

6 ES6 map

let array = [1,2,3,4,21,2,333,12,33,44,55,1,2,3,4,5]       

let newArr = []        

let map = new Map()        

array.forEach(function(item,index){            

    if(map.has(item))    {                

        map.set(item,true)         

   }else{            

        map.set(item,false)                

        newArr.push(item)         

   }        

})       

 console.log(newArr)