Automatically create object if undefined

Question

Is there an easy way to automatically add properties to objects if they don\'t allready exist?

Consider the following example:

var test = {}
test.hel         


        

Answer 1

New object

myObj = {};

recursive function

function addProps(obj, arr, val) {

    if (typeof arr == 'string')
        arr = arr.split(".");

    obj[arr[0]] = obj[arr[0]] || {};

    var tmpObj = obj[arr[0]];

    if (arr.length > 1) {
        arr.shift();
        addProps(tmpObj, arr, val);
    }
    else
        obj[arr[0]] = val;

    return obj;

}

Call it with a dot notated string

addProps(myObj, 'sub1.sub2.propA', 1);

or with an array

addProps(myObj, ['sub1', 'sub2', 'propA'], 1);

and your object will look like this

myObj = {
  "sub1": {
    "sub2": {
      "propA": 1
    }
  }
};

It works with non-empty objects too!