Creating objects in for loop. I missing the mark a bit

Question

I would like to have a for loop create objects as the children of a parent object. Usually, I would declare the object without using the for loop like this:

 var mObj = {};
 mObj.obj1 = {};
 mObj.obj2 = {};
 mObj.obj3 = {};
 mObj.obj3.firstname = "john";
 mObj.obj3.lastname = "superfly";

Now lets say I would like to employ a for loop to create the children objects of a parent object "mObj".

This is where I am going wrong:

var mArr = ["firstname","lastname","email"]; // This array holds the keys for the   objects

 var mObj = {};

 var len = (mArr.length);

 for(var i=0; i<len; i++){

      var obj+i = {}
      mObj = obj+i;
      mObj.obj + i.mArr[i] = ""

    }

So the outcome of this would be:

 mObj.obj1.firstname = "";
 mObj.obj2.lastname = "";
 mObj.obj3.email = "";

I just cannot seem to name the object with counter that is being created within for loop like:

obj1
obj2
obj3

Any help would highly be appreciated.

Thanks.

Matt · Accepted Answer · 2012-04-17 18:52:25Z

1

var obj+i = {} is invalid syntax.

Try this:

mObj['obj' + i] = {};

If i == 1, this gives mObj['obj1'] = {};

Which is equiavlent to:

mObj.obj1

But when constructing dynamically, you have to use the

mObj['obj' + i]

Formatting.

answered Apr 17, 2012 at 18:52

Matt

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1 Comment

Combustion007 Over a year ago

thanks a lot. After some elbow grease, I got it going. I spend hours trying things out that darn . syntax was throwing me off.

SeanCannon · Accepted Answer · 2012-04-17 18:53:16Z

1

var mArr = ["firstname","lastname","email"],
    mObj = {},
    len  = (mArr.length),
    i    = 0;

 for(; i<len; i++){
      myObj['obj' + i] = {}
      myObj['obj' + i].mArr[i] = ""
  }

answered Apr 17, 2012 at 18:53

SeanCannon

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Comments

Tejs · Accepted Answer · 2012-04-17 18:52:36Z

0

You need to use the bracket syntax to assign a dynamic variable. For example:

var sampleObj = {};

for(var j = 0; j < 3; j++)
{
    sampleObj["obj" + j] = { test: j };
}

This should produce the following object:

{
    "obj1" : { test: 1 },
    "obj2" : { test: 2 },
    "obj3" : { test: 3 }
}

After running the loop then, you could validly use this statement:

var testVal = sampleObj.obj1.test;

answered Apr 17, 2012 at 18:52

Tejs

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1 Comment

Combustion007 Over a year ago

var keyArr = ["firstname","lastname","email"] var valArr = ["John","Superfly","[email protected]"]; mObj = {}, len = (mArr.length), i = 0; for(; i<len; i++) { mObj['obj' + i] = {}; mObj['obj' + i][mArr[i]] = valArr[i]; } console.log(mObj.obj2.email);

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