indexOf syntax for multidimensional arrays?

Question

What is the syntax for indexOf() to go through a multidimensional array? For instance:

var x = [];
// do something
x.push([a,b]);

x.indexOf(a) // ??

I want to find 'a' and do something with 'b'. But it does not work... As this method should be iterative itself, I do not presume using any other iteration would be a good thing to do. Currently I simulate this using 2 simple arrays but I guess this should somehow work too...

Answer 1

JavaScript does not have multidimensional arrays as such, so x is merely an array. Also, the indexOf method of Array is not supported in all browsers, in particular IE (up to version 7, at least), only being introduced in JavaScript 1.6.

Your only option is to search manually, iterating over x and examining each element in turn.

Answer 2

Unless you want to preserve order, it's much simpler to use a dictionary:

var x = {};

// do something

x[a] = b;

You can still iterate over the keys, although the order is undefined:

for (var key in x) {
   alert(x[key]);
}

Answer 3

x[ x.indexOf(a) ]

This will only work with ordered objects/lists and only if Array.prototype.indexOf is defined.

x = [1,2], b = {one:function(){alert('gj')}}, c = x.push(b);

x[ x.indexOf( b ) ]['one']()

Answer 4

You could use a an object (or dictionary) as Philippe Leybaert suggested. That will allow quick access to elements:

var x = {};

x[a] = b; // to set

alert(x[a]) // to access

But if you insist on using indexOf, there's still a way, however ugly it is:

var x = [];

var o = Object(a); // "cast" to an object
o.b = b; // attach value

x.push(o);

alert(x.indexOf(a)); // will give you the index
alert(x[1].b); // access value at given index

Answer 5

So, basically, it is not doable. The Object way is unnecessarily complicated in this case, I want to stick with indexOf because of its simplicity, therefore I will keep my two arrays. Thanks to everyone of course.

Answer 6

Simply: indexOf() does not work this way. It might work if you did something like this:

var x = [];
// do something
z = [a,b];
x.push(z);

x.indexOf(z);

But then you'd already have z.b wouldn't you? So if you must ignore the advice of everyone who thinks that using an object (or dictionary) is actually easier you'll have to either use Ates Goral's approach, or search for the index yourself:

Array.prototype.indexOf0 = 
  function(a){for(i=0;i<this.length;i++)if(a==this[i][0])return i;return null;};
var x = [];
// do something
x.push([a,b]);

x.indexOf0(a); //=> 0