Call Javascript object with string variable

Question

If I have a javascript object like this...

window.object = 
{
    "Element1" :
    {
        "startDate" : "-1m",
        "endDate" : "0d"
    }
};

I can use the below code to alert out -1m...

alert(object.Element1.startDate);

However, what if Element1 was given to me through a parameter as a string. How could I get the same result if I have to use a variable? Like this but not correct...

var elementId = this.id;
alert(object.elementId.startDate);

and [Dynamic object property name](http://stackoverflow.com/q/4244896/218196) — Felix Kling, Sep 09 '13 at 19:12

score 5 · Accepted Answer · answered Sep 09 '13 at 19:12

5

Try this:

object[elementId].startDate

Or if id is a number , this will work:

object["Element"+elementId].startDate

answered Sep 09 '13 at 19:12

Ivan Chernykh

41,617
13
134
146

your first answer captures all cases – Yaw Boakye Sep 09 '13 at 19:14
Console is catching an error, object[elementId] is undefined – gmustudent Sep 09 '13 at 19:16
@gmustudent so something wrong with your `this.id` and as result after this part: `var elementId = this.id;` your `elementId` is undefined – Ivan Chernykh Sep 09 '13 at 19:18
Sorry. unrelated issue to why I had a problem. Will accept after time limit – gmustudent Sep 09 '13 at 19:22
@Yaw i'm just right now reading about `Objects` in Douglas Crockford' book , that is my little secret ;) – Ivan Chernykh Sep 09 '13 at 19:24

score 1 · Answer 2 · answered Sep 09 '13 at 19:26

1

You can use the global object this:

var Element1 = 'boo';

var stringname = 'Element1';
alert(this[stringname]);

A second, hacky, method, is that javascript can print javascript and that printed javascript will also be interpreted.

answered Sep 09 '13 at 19:26

neonKow

29
4

If you use `window` instead of `this`, you can access global variables everywhere not only in global scope. What do you mean by *"javascript can print javascript and that printed javascript will also be interpreted"*? Could you provide an example? – Felix Kling Sep 09 '13 at 19:30
If you do `document.write('alert("boo");');`, it will give you an alert. Breaking up the script tag may or may not be necessary depending on context, I believe. – neonKow Sep 09 '13 at 20:19

Call Javascript object with string variable

2 Answers2