The basic method of the JavaScript array deduplication

Method 1: double for the cycle to re-
loop through the array in each unit cell is compared with that later, if the same unit after it's deleted
Note: To prevent the collapse of the array

        var arr = [1,1,1,2,2,2,3,3,3,4,4,4,5,5,5];
        for(let i = 0 ; i <= arr.length-1 ; i++){
            for(let j = i+1 ; j <= arr.length-1 ; j++){
                if(arr[i] === arr[j]){
                    arr.splice( j , 1 );
                    j--;
                }
            }
        }
        console.log(arr);

Method 2: value of sorting the array, two adjacent unit compares
long as a weight for loop

var arr = [1,2,3,4,5,1,2,3,4,5,1,2,3,4,5];
arr = arr.sort(function(a,b){return a-b});
for(let i = 0 ;  i <= arr.length-1-1 ; i++){
    if(arr[i] === arr[i+1]){
        arr.splice(i+1 , 1);
        i--;
    }
}
console.log(arr);

Method 3: Using the object, the name of the same key can not be stored

  var arr = [1,2,3,4,5,1,2,3,4,5,1,2,3,4,5];
    const obj = {};

    arr.forEach(function(val,key){
        obj[val] = '随便';
    });

    const newArr = [];
    for(let key in obj){
        newArr.push(key); 
    }

    console.log(obj);
    console.log(newArr);

Method 4: indexOf method of
determining the value to be written, whether already present in the new array

   var arr = [1,2,3,4,5,1,2,3,4,5,1,2,3,4,5];

    const newArr = [];

    for(let i = 0 ; i <= arr.length-1 ; i++){
        if( newArr.indexOf(arr[i]) == -1 ){
            newArr.push(arr[i]);
        }
    }

    console.log(newArr);

Method 5: array unit, the data type assigned to SET
the same data type SET does not store data, automatically deduplication

var arr = [1,2,3,4,5,1,2,3,4,5,1,2,3,4,5];

const set = new Set(arr);

const newArr = [...set];

const newArr = [...new Set(arr)];

console.log(newArr);