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

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

Answer 2

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 3

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]);
}