Using a variable value to call an array element

Question

I have a string variable which contains the name of an array. What I\'d like to do is access an element of that array. And write it to another variable. How can I do this?

Answer 1

This should do it:

    var sample = new Array();
    sample[0] = 'one';
    sample[1] = 'two';

    var arrayname = "sample";
    var number = window[arrayname][1];
    alert(number);

Answer 2

var sample = new Array();
sample[0] = 'one';
sample[1] = 'two';
var obj = {"sample": sample}

var arrayname = "sample";
var number = obj[arrayname][1];

Answer 3

I mean you can use eval, but it is not the best approach:

eval("var arrayname = sample");
var number = arrayname[1];  

Why not just do:

var arrayname = sample;
var number = arrayname[1];  

Answer 4

There's no universal way in JavaScript to do exactly what you've got set up there, but you can use string variables to access object properties in a dynamic way.

var objArr = { array1: [], array2: [] };

Now you can use a variable with the value "array1" or "array2" to get at those arrays:

var name = "array2";
objArr[name].push(14);

What you cannot do in JavaScript is access local variables by a dynamic name, or indirectly if you prefer. You can access global variables that way if you have a name for the global context, which in a browser is the window object:

window[ name ].push(17);

However there's no way to get a similar name for a local scope.

edit — @Neal points out (and is downvoted mercilessly) that eval() can do what you want, but a lot of people recommend staying far away from eval() unless it's absolutely unavoidable (which is really rare). I've trained myself to ignore it so well that I always forget about it when questions like this are asked (which is, oddly, quite often on SO, though in my programming practice I never find myself wanting to do this).

Answer 5

You could use something like:

var arrayName = "sample",
    number = window[arrayname][1];

Answer 6

Out of my head...

First declare some global variable

var buf;

Then

var sample = new Array();
sample[0] = 'one';
sample[1] = 'two';

var arrayname = "sample";
eval('buf=' + arrayname + ';');
var number = buf[1];

Damn undesirable way but does what you want...