JS implementation of array de-weight method Summary (six methods)

Method One:

Two-layer loop, outer loop element, inner loop comparison value

If the same value is skipped, not the same, push into the array

Array.prototype.distinct =function(){ vararr = This, result=[], I, J, Len=arr.length; for(i = 0; i < Len; i++){   for(j = i + 1; j < Len; J + +){   if(Arr[i] = = =Arr[j]) {J= ++i; }} result.push (Arr[i]); } returnresult;}varARRA = [1,2,3,4,4,1,1,2,1,1,1];arra.distinct (); //back to [3,4,2,1]

Method two: Using splice to operate directly in the original array

Two-layer loop, outer loop element, inner loop comparison value

If the value is the same, delete the value

Note: After you delete an element, you need to reduce the length of the array by 1.

Array.prototype.distinct =function (){ vararr = This, I, J, Len=arr.length; for(i = 0; i < Len; i++){   for(j = i + 1; j < Len; J + +){   if(Arr[i] = =Arr[j]) {Arr.splice (J,1); Len--; J--; }  } } returnarr;};varA = [1,2,3,4,5,6,5,3,2,4,56,4,1,2,1,1,1,1,1,1,];varb =a.distinct (); Console.log (b.tostring ());//1,2,3,4,5,6,56

Advantages: Easy to understand

Cons: High memory consumption, slow speed

Method Three: Using the properties of the object can not be the same characteristics to go to the weight

Array.prototype.distinct =function (){ vararr = This, I, obj={}, result=[], Len=arr.length; for(i = 0; i< arr.length; i++){  if(!obj[arr[i]]) {//If you can find it, it proves that the array element repeats.Obj[arr[i]] = 1;  Result.push (Arr[i]); } } returnresult;};varA = [1,2,3,4,5,6,5,3,2,4,56,4,1,2,1,1,1,1,1,1,];varb =a.distinct (); Console.log (b.tostring ());//1,2,3,4,5,6,56

Method Four: Array recursion weight

Using the idea of recursion

Sort first, then compare from the last, encounter the same, then delete

Array.prototype.distinct =function (){ vararr = This, Len=arr.length; Arr.sort (function(A, B) {//sorting arrays for easy comparison  returnAb;}) functionLoop (index) {if(Index >= 1){   if(Arr[index] = = = Arr[index-1]) {arr.splice (index,1); } Loop (Index-1);//recursive loop function for de-weight}} loop (Len-1); returnarr;};varA = [1,2,3,4,5,6,5,3,2,4,56,4,1,2,1,1,1,1,1,1,56,45,56];varb =a.distinct (); Console.log (b.tostring ()); //1,2,3,4,5,6,45,56

Method Five: Using IndexOf and foreach

Array.prototype.distinct =function (){ vararr = This, result=[], Len=arr.length; Arr.foreach (function(V, I, arr) {//The Map,filter method can also be used here to achieve  varBOOL = Arr.indexof (v,i+1);//start looking for duplicates from the next index value passed in the parameter  if(bool = = =-1) {Result.push (v); } }) returnresult;};varA = [1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,3,3,3,3,3,3,3,2,3,3,2,2,1,23,1,23,2,3,2,3,2,3];varb =a.distinct (); Console.log (b.tostring ());//1,23,2,3

Method Six: Using the set of ES6

A set data structure, similar to an array, whose member values are unique.

Convert set structure to an array using Array.from

functionreturn array.from (new  Set (Array));} Dedupe ([[+]

Expand Operator (...) Internal use of For...of loops

Let arr = [1,2,3,3= [...] New  //[[+]

The following is an introduction to the method of merging arrays and going to heavy

One, concat () method

Idea: the Concat () method merges an incoming array or non-array value with the original array, forming a new array and returning it. The method produces a new array.

function Concatarr (arr1, arr2) {  var arr = arr1.concat (arr2);   = Unique1 (arr); // and then refer to any of the above methods  of de-weight return arr;}

Second, Array.prototype.push.apply ()

Idea: The advantage of this method is that it does not produce a new array.

var a = [1, 2, 3]; var b = [4, 5, 6]; Array.prototype.push.apply (A, b); // a=[1,2,3,4,5,6] // equivalent to: A.push.apply (A, b); //  function  concatarray (arr1,arr2) {  Array.prototype.push.apply (arr1, arr2);   = unique1 (arr1);   return arr1;}

　　

JS implementation of array de-weight method Summary (six methods)