Accessing JavaScript object via key

Question

I have a JavaScript object called data. I am using the following code to sort the keys in the object :

var index = [];

// build the index
for (var x in data) {
    index.push(x);
}

// sort the index
index.sort(function (a, b) {
    return a == b ? 0 : (a > b ? 1 : -1);
});

I then want to access the value for a particular index key in the following way :

for (var i=0; i<index.length; i++) {
    var key = index[i];
    document.getElementById(key).value = data.key;
}

However I am getting undefined for the data.key value. Can anyone suggest why ?

I've edited out the "JSON" term from your question. JSON implies a string: if you can loop it with a for() construct, it can't be a string. — Álvaro González
– Álvaro González, Commented Aug 29, 2013 at 8:24

Sirko · Accepted Answer · 2013-08-29 08:23:13Z

3

Change to

document.getElementById(key).value = data[key];

If the key you want to access is stored within a variable, you have to use the bracket notation. In your code, JavaScript will search for a key named "key" and thus fails.

Example:

var key = 'test';

console.log( data.key );  // yields content of data.key
console.log( data[key] ); // yields content of data.test

edited Aug 29, 2013 at 8:23

answered Aug 29, 2013 at 8:17

Sirko

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1 Comment

Álvaro González Over a year ago

To clarify: the document object is part of the DOM so it's used to manipulate HTML documents, not JavaScript objects.

Sgoldy · Accepted Answer · 2013-08-29 08:17:13Z

0

How about

Object.keys(data)[key] ?

Not sure it would work, without showing the structure of data.

edit: This way retrieves object key according to numerical index (0,1...,n), and not by name.

answered Aug 29, 2013 at 8:17

Sgoldy

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