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.