4 ways to remove repeating elements in an array in JS

Working on this problem today, trying multiple methods is unsatisfactory, so write a blog to summarize how to remove duplicate elements in JS.

Method 1:

        array.prototype.method1 = function () {             var arr[];    //defining a temporary array             for (var i = 0; i  < this.length; i++) {    //loops through the current array                  //determines whether the element labeled I in the current array has been saved to a temporary array                  //if it is already saved, skip it, or save this element in a temporary array                  if (Arr1.indexOf (This[i]) &NBSP;==&NBSP;-1) {                     arr.push (This[i]);                 }            }             return arr;         }

    Method 2:

                 Array.prototype.method2 = function () {             var h{};    //Define a hash table              var arr[];  //defines a temporary array                          for (var i  = 0; i < this.length; i++) {    //loops through the current array                  //the element to see if it already exists in the table, Skip if present, otherwise deposit in temporary array                  if (!h[this[i]) {                     //Deposit Hash Table &Nbsp;                    h[this[i]] = true;                     //the current array elements into a temporary array                      arr.push (This[i]);                 }             }             return arr;        }

    Method 3:

        array.prototype.method3 = function () {             //directly define the result array              var arr[this[0]];             for (var i = 1; i < this.length; i++) {     //loops through this array starting from the second item of the array                  //the elements to be judged:                 //if the current element of the array appears in this array for the first time, the position is not i                 //then we can judge that the element i is repeating, otherwise it will be deposited directly into the result array                  if (This.indexof (this[i])  == i) {         &nBsp;           arr.push (This[i]);                 }             }             return arr;                 }

    Method 4:

        array.prototype.method4 = function () {             //to sort the array              this.sort ();             //defining the result array             var arr[this[ 0]];            for (var i = 1;  i < this.length; i++) {    //iterates through the array from the second item of the array                  //determines whether adjacent two elements are equal, or writes an element to an array of results if the data is duplicated for equality                 if (This[i] &NBSP;!==&NBSP;ARR[ARR.LENGTH&NBSP;-&NBSP;1]) {                &nbsP;    arr.push (This[i]);                 }                         }             return arr;                     }

For example:

var arr = [112,112, 34, ' Hello ', 112,112, 34, ' hello ', ' str ', ' str1 ']; Alert (arr.method3 ());

Both Method 1 and Method 3 use the IndexOf () method of the array, which is used primarily to find where the element first appears in the array. Compare waste of resources and time.

Method 2 uses a hash table to write the elements that have already appeared in the subscript form into an object, and the subscript reference is less time-saving than searching with the array indexof () method.

Method 4 is to sort the array first, then compare the values of the adjacent two elements one at a time, using the JS native sort () method.

Readers can write their own program to test the efficiency of the four methods. For example: first, using random function to generate a 50000-length random number array, and then four methods to execute, recording program run time to compare the advantages and disadvantages of four methods.

4 ways to remove repeating elements in an array in JS