Check if an array is inside an array

Question

The title should explain my question.

I have an array:

a = [[1,2],[1,3],[1,4]]; 

How can I check if the array [1,2] is inside the array a?

Answer 1

That depends on the situation.

given

var a = [1,2], b = [1,3], c = [a,b]; 

We can check easily if a resides in c, if we have c to test on.

for(var i=0,d;d=c[i];i++) { if(d === a) { //a is inside c } } 

or even simpler for browser that supports it (ie7 doesn't)

if(c.indexOf(a) != -1) { //a is inside c } 

But if we only have a, and a is not a local variable and we wish to know if it exists inside any array, then we can't, since a is a reference to an object and we can't possibly know if a reference to it exists elsewhere outside our current scope.

Answer 2

if you have a reference, the you can use the == operator. else you have to write your own method to test values. something like this:

function someMethod(testArr, wanted){ for (i=0; i<testArr.length; i++){ if(array_diff(testArr[i], wanted).length==0 && array_diff(wanted, $subArr).length==0){ return true; } } return false; } function array_diff(a1, a2) { var a=[], diff=[]; for(var i=0;i<a1.length;i++) a[a1[i]]=true; for(var i=0;i<a2.length;i++) if(a[a2[i]]) delete a[a2[i]]; else a[a2[i]]=true; for(var k in a) diff.push(k); return diff; } 

Answer 3

If your array contains numbers or texts only, you can join each array into string, then compare if a string is inside the other.

var a = [[1,2],[1,3],[1,4]]; var b = [1,2] var aStr = '@' + a.join('@') + '@' var bStr = '@' + b.join() + '@' if (aStr.indexOf(bStr) > -1){ alert ('b is inside a') }else{ alert ('b is not inside a') } 

Answer 4

You can try this if your array elements are non-nested arrays.

return JSON.stringify([[1,2],[1,3],[1,4]]).indexOf(JSON.stringify([1,2])) > 0 

This checks if the JSON representation of [1,2] is contained in the JSON representation of [[1,2],[1,3],[1,4]]

But in this case it gives a false positive

return JSON.stringify([[[1,2]],[1,3],[1,4]]).indexOf(JSON.stringify([1,2])) > 0 

returns true.

Answer 5

You can also loop through the array object and for each of it's item you can use jQuery.isArray() to determine if the object is an array.