Adding custom variables to an object

Question

Suppose I have an object obj which has some variables in it. What I want to do is to add a new variable which has a name i gave as a parameter. For example:

var obj=
{
  number:8
}

function AddField(field_name,obj)
{
  //some magical code here
}

If I call

AddField('name',obj);

i want to be able to do

obj.name='Apple'

after calling this function.

Any ideas?

You could always just call `obj.name = 'Apple'`, if you'd tried it, you'd know it works — zzzzBov, May 14 '13 at 13:26

score 5 · Answer 1 · answered May 14 '13 at 13:25

5

Use square brackets notation:

obj[field_name] = value;

REF: http://www.jibbering.com/faq/faq_notes/square_brackets.html#vId

answered May 14 '13 at 13:25

VisioN

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1

OP doesn't seem to want to add a value, just a field. – Denys Séguret May 14 '13 at 13:25
@dystroy Then `value = undefined`. – VisioN May 14 '13 at 13:26
Maybe. In fact I don't get what's the real question. – Denys Séguret May 14 '13 at 13:27
So simple, yet perfect for my need, thank you. I will accept the answer as soon as i can. – AutomaticHourglass May 14 '13 at 13:27

score 0 · Answer 2 · answered May 14 '13 at 13:25

0

Use the bracket notation:

obj[field_name] = void 0;

This creates a new property with an undefined value.

answered May 14 '13 at 13:25

Ja͢ck

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score 0 · Answer 3 · answered May 14 '13 at 13:29

If obj is already defined, you can just do obj.field_name = null or obj["field_name"] = null. I wouldn't set any value to undefined even though the language allows for that, simply for a semantic issue: undefined means "this property/variable has not been defined" and null means "this property/variable has no value".

Adding custom variables to an object

3 Answers3