Question

I just want the data in this way:

var _2dimen = {};

_2dimen['window1']['panel1'] = '2010-10-01'
_2dimen['window1']['panel2'] = '2010-10-01'
...
_2dimen['window3']['panel1'] = '2010-10-01'

which window and panel number are dynamic.It means I could using the pattern of :
I mean: the variable of window and panel is dynamic create in my situation,the window may be window1 or window2… and panel may be panel2,panel4.

var window = windowNumber, panel= panelNumber;

_2dimen[window][panel] = 'some date here';

How can I struct the code to assign and edit the value?

the code I wrote just what I was thought it maybe,it didn’t work!!
_2dimen[window] = ‘data’ work fine and I adding the [panel]

 _2dimen[window][panel] = 'data' the firebug prompts me that :

_2dimen[window] is undefined
     _2dimen[window][panel] = date; 

Thank you very much!

Answer 1

What some call “associative arrays” in JS are just objects:

var twoD = { window1: {
    panel1: '2010-10-01',
    panel2: '2010-10-02',
    ...
  }, 
  window3: {
    panel1: '2010-12-01',
    ...
  }
};

If you’re actually naming the indices things like ‘window1’ and ‘panel2’, a better approach would be to use arrays. This way, you can loop over panels and windows, yet still set other properties on the top level object and windows.

var twoD = { windows: [
    { panels: ['2010-10-01', '2010-10-02', ...
    ...
    // window3
    { panels: ['2010-12-01']}
  ],
  foo: 'bar'
};
...
twoD.windows[0].panels[1] // '2010-10-02'

And remember, identifiers can’t start with a digit.

If the panels set on windows skip some indices, you can do that, too. Note that you can’t set properties of an undefined value. _2dimen[window][panel]={} fails when _2dimen[window] is undefined. You need to test & set the element at the major index before accessing an element at a minor index.

function TwoD() {
    this.windows = [];
}
TwoD.prototype.window = function(i) {
    if (! this.windows[i]) {
        this.windows[i] = {panels: []};
    }
    return this.windows[i];
};
...
var wall = new TwoD();
wall.window(2).panels[1] = '2010-12-02';

This is very close to your current implementation, but has the advantage of allowing iteration over windows & panels when other properties are set.