JQuery Disjoint

Question

I have two arrays:

var a = new Array(1,2,3,4); var b = new Array(5,3,2,6); 

I want to know which elements are in array a , but not in array b and which elements are in b but not in a ?

I know that one way is to go through them each, but is there a more efficient way?

Thank you for your time.

Answer 1

You can try the following:

 var aNotInB = $.grep(a, function($e) { return $.inArray($e, b) == -1; }); var bNotInA = $.grep(b, function($e) { return $.inArray($e, a) == -1; }); 

You can define this as a jquery function:

 $.disjoin = function(a, b) { return $.grep(a, function($e) { return $.inArray($e, b) == -1; }); }; var aNotInB = $.disjoin(a,b); var bNotInA = $.disjoin(b,a); 

Answer 2

You should look at each element of both arrays to get the difference between them. So there is no other way than iterating over both arrays:

 Array.prototype.diff = function(otherArray) { var diff = [], found; for (var i=0; i<this.length; i++) { found = false; for (var j=0; j<otherArray.length; j++) { if (this[i] == otherArray[j]) { found = true; break; } } if (!found) { diff.push(this[i]); } } return diff; }; var a = [1,2,3,4], b = [5,3,2,6]; var aDiffB = a.diff(b), bDiffA = b.diff(a); 

You can skip some comparisons when sorting arrays and start with an inner loop with the element after the last match and break it if the value is greater:

 Array.prototype.diff = function(otherArray) { var diff = [], found, startAt = 0, a = this.sort(), b = otherArray.sort(); for (var i=0; i<a.length; i++) { found = false; for (var j=startAt; j<b.length; j++) { if (a[i] > b[j]) { break; } if (a[i] == b[j]) { found = true; startAt = j + 1; break; } } if (!found) { diff.push(a[i]); } } return diff; }; 

But sorting both arrays is also worth it.

Answer 3

The PHP in_array () function was ported to Javascript some time ago. I used it from time to time. In addition, the array_diff () function has also been ported over .

 function in_array(needle, haystack, argStrict) { // http://kevin.vanzonneveld.net var key = '', strict = !!argStrict; if (strict) { for (key in haystack) { if (haystack[key] === needle) { return true; } } } else { for (key in haystack) { if (haystack[key] == needle) { return true; } } } return false; } function array_diff() { // * example 1: array_diff(['Kevin', 'van', 'Zonneveld'], ['van', 'Zonneveld']); // * returns 1: ['Kevin'] var arr1 = arguments[0], retArr = {}; var k1 = '', i = 1, k = '', arr = {}; arr1keys: for (k1 in arr1) { for (i = 1; i < arguments.length; i++) { arr = arguments[i]; for (k in arr) { if (arr[k] === arr1[k1]) { // If it reaches here, it was found in at least one array, so try next value continue arr1keys; } } retArr[k1] = arr1[k1]; } } return retArr; } 

Answer 4

you can sort them first ( a.sort() ) and then this is a simple iteration.