How to dynamically create obj property in javascript?

Question

I want to create a JSON like this:

{
   '2014-1-1':
             {
             'objA':
                   {
                        'attrA': 'A'
                        'attrB': 'B'
                   }
             }

}

I tried:

  obj['2014-1-1'] = {'objA' : { 'attrA' : 'A'}};

  obj['2014-1-1'] = {'objA' : { 'attrB' : 'B'}};

But I only see B value on my object now, I guess 'because 'objA' is being overridden, how do I add 'attrA' and 'attrB' both for objA ?

tymeJV · Accepted Answer · 2014-12-14 02:19:23Z

1

Once the property exists, simply access it and set a value, don't overwrite:

obj['2014-1-1'] = {'objA' : { 'attrA' : 'A'}};
obj['2014-1-1']['objA']['attrB'] = 'B';

You'd probably just want to make a check to see if the property exists, if not, create it, then assign:

if (!obj['2014-1-1'].hasOwnProperty('objA')) {
    obj['2014-1-1']['objA'] = {}
}

obj['2014-1-1']['objA']['attrA'] = 'A';
obj['2014-1-1']['objA']['attrB'] = 'B';

answered Dec 14, 2014 at 2:19

tymeJV

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3 Comments

user1701840 Over a year ago

what if I don't know if 'objA' exist?

tymeJV Over a year ago

Use the hasOwnProperty method to check for existence: if (obj['2014-1-1'].hasOwnProperty('objA'))

Jonast92 Over a year ago

@user1701840 You make a check?

Roco CTZ · Accepted Answer · 2014-12-14 02:20:56Z

0

It's not working because you are overwriting the object. You can do it like this:

obj['2014-1-1'] = {'objA' : { 'attrA' : 'A', 'attrB' : 'B'}};

attrA and attrB are two different properties of objA so this way you set both of them.

answered Dec 14, 2014 at 2:20

Roco CTZ

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