Monday, August 12, 2013

Get unique/distinct values from an array using JQuery $.grep and $.inArray

Consider an example of getting unique elments from an array a = [1,1,2,3,8,2]

Array.prototype.unique = function(){
    var array = this;
    return array.filter(function(ele, index, arr){
        return index == arr.indexOf(ele);
    });
}
and in our Javascript,

var array = [1,1,2,3,8,2];
var uniqueElments = arrray.unique();

//Output will be 1,2,3,8
But the issue is few of the older version browsers including IE7 that doesn't support some array features - such as indexOf or filter, so we can use jquery functionalities like:

  •     use $.grep instead of Array.filter
    • The $.grep() method removes items from an array as necessary so that all remaining        items pass a provided test. The test is a function that is passed an array item and the index of the item within the array. Only if the test returns true will the item be in the result array.
  • use $.inArray instead of Array.indexOf
    • The $.inArray() method is similar to JavaScript's native .indexOf() method in that it returns -1 when it doesn't find a match. If the first element within the array matches value, $.inArray() returns 0.
Now here's how the changed code would look like:

Array.prototype.unique = function(){
    var array = this;
    return $.grep(array, function(ele, index){
            return $.inArray(ele, array) === index;
    });
}
References:
$.grep
$.inArray
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