JS array deduplication

You have no time to test the following items, and you do not have time to implement them on your own. Record them first.

// First add the indexof and lastindexof methods to the array object prototype. (if not,) if (! Array. prototype. indexof) {array. prototype. indexof = function (element, index) {var length = This. length; If (Index = NULL) {Index = 0;} else {Index = + index | 0; If (index <0) index + = length; if (index <0) Index = 0;} For (VAR current; index <length; index ++) {current = This [Index]; If (current = element) return Index;} return-1 ;}} if (! Array. prototype. lastindexof) {array. prototype. lastindexof = function (element, index) {var length = This. length; If (Index = NULL) {Index = length-1;} else {Index = + index | 0; If (index <0) index + = length; if (index <0) Index =-1; else if (index> = length) Index = length-1;} For (VAR current; index> = 0; index --) {current = This [Index]; If (current = element) Return Index;} return-1 ;}// common implementation method var arrayunique1 = function (ARR) {for (VAR I = 0, Len = arr. length, result = [], item; I <Len; I ++) {item = arr [I]; If (result. indexof (item) <0) {result [result. length] = item ;}} return result ;}// use the lastindexof and splice methods to implement var arrayunique2 = function (ARR) {var length = arr. length; while (-- length) {// if it already exists, delete the element at this position if (ARR. lastindexof (ARR [length], length-1)>-1) {arr. splice (length, 1) ;}} return arr ;}

Test Results
Test data: var arr = [2,232,];
IE7 cycles 10,000 times:
Arrayunique1 is 460 ms, and arrayunique2 is 190 ms.
Ff3.5 cycles 100,000 times:
Arrayunique1 is 170 ms, and arrayunique2 is 63 MS.

Other implementation methods
In addition to the implementation method in 2 described above, there are actually other implementation methods. Jquery provides an implementation method. Let's take a look at the specific code:

unique: function( array ) {    var ret = [], done = {};    try {        for ( var i = 0, length = array.length; i < length; i++ ) {            var id = jQuery.data( array[ i ] );            if ( !done[ id ] ) {                done[ id ] = true;                ret.push( array[ i ] );            }        }    } catch( e ) {        ret = array;    }    return ret;}

From: http://www.welefen.com/javascript-array-unique.html

 

Array. prototype. delrepeat = function () {var newarray = new array (); var Len = This. length; For (VAR I = 0; I <Len; I ++) {for (var j = I + 1; j <Len; j ++) {If (this [I] === this [J]) {J = ++ I ;}} newarray. push (this [I]);} return newarray;} // but it is obvious that the for loop is embedded with another for loop. It must be time-consuming for a large amount of data! Inefficient! After searching and expert guidance, a new method is optimized: array. prototype. delrepeat = function () {var newarray = []; var provisionaltable ={}; for (VAR I = 0, item; (item = This [I])! = NULL; I ++) {If (! Provisionaltable [item]) {newarray. Push (item); provisionaltable [item] = true ;}} return newarray ;}

From: http://www.css88.com/archives/2429