Javascript: Using object's field's value to determine another object literal's field's name

Question

I want to use object's field's value while creating another object using literal notation:

var T = {
 fieldName : 'testField'
};
/*
// Doesn't work.
var test = {
 T.fieldName : 'value'
};
*/
// Does work.
var test = [];
test[T.fieldName] = 'value';
alert(test.testField);          // test

But it doesn't work.
Is there a way to solve this issue or using square brackets is the only way out?

Upd.: Removed non-working code.

You haven't tried to run the code you posted, have you?

thorn0
– thorn0

2009-12-21 11:12:45 +00:00
Commented Dec 21, 2009 at 11:12 — thorn0
– thorn0, Commented Dec 21, 2009 at 11:12
Oops, it somehow seemed to work for me. Removed wrong code.

Li0liQ
– Li0liQ

2009-12-21 11:23:42 +00:00
Commented Dec 21, 2009 at 11:23 — Li0liQ
– Li0liQ, Commented Dec 21, 2009 at 11:23

Marius · Accepted Answer · 2009-12-21 11:13:22Z

2

var T = {
 fieldName : 'testField'
};
var dummy = T.fieldName;        // dummy variable
var test = {
 dummy : 'value'
};
alert(test.testField);          // test

That should not work. The value 'value' will be stored in test.dummy, not test.testField. The way to do it would be:

var T = {
 fieldName : 'testField'
};
// Does work.
var test = {};
test[T.fieldName] = 'value';
alert(test.testField);          // alerts "value"

Which is what you already have

answered Dec 21, 2009 at 11:13

Marius

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1 Comment

Li0liQ Over a year ago

It somehow seemed to work for me :). Tested and removed it from the question as wrong code.

Beresta · Accepted Answer · 2009-12-21 11:21:43Z

2

Your "test" variable is Array, not Object.

You should create "test" like "= {}" instead of "= []".

answered Dec 21, 2009 at 11:21

Beresta

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Comments

RameshVel · Accepted Answer · 2009-12-21 11:35:13Z

0

One possible way is.

var T={
    testField : 'testField'
};

     eval ('var test = {' + T.testField + ':' +  value + '}');

And you make this generic, something like this

function MakeVar(varName,fieldToUse,valueToPass)
{
      var res = 'var ' +varName+ '= {' + T.testField + ':' +  value + '}'
     eval(res);
}

var T={
    testField : 'testField'
};


     MakeVar('test',T.testField,'value');
     var outt=test.testField;

Hope this helps

answered Dec 21, 2009 at 11:35

RameshVel

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