JavaScript: Assign value to object from string

Introduction and disclaimer

Some time back I found myself in need of a way to take a string from dot notation contacts.name.first and build/update an object from that.

I scoured the internet and found several methods, none of which quite did what I needed them to do; some would only update an existing object, while others would only create a new object. Most only worked down to a handful of levels.

I took what I found and used them as a reference to create this handy method. Very little of this method is purely my brainchild, but rather a combination of help from the geniuses that troll StackOverflow.

I also want to admit that there are likely other ways to go about this exact same thing, some may even be more elegant.

String toObject

String.prototype.toObject = function( obj, value ) {
  var names = this.split('.');
  // If a value is given, remove the last name and keep it for later:
  var lastName = arguments.length === 2 ? names.pop() : false;
  // Walk the hierarchy, creating new objects where needed.
  // If the lastName was removed, then the last object is not set yet:
  for( var i = 0; i < names.length; i++ ) {
    obj = obj[ names[i] ] = obj[ names[i] ] || {};
  }
  // If a value was given, set it to the last name:
  if( lastName ) obj = obj[ lastName ] = value;
  // Return the last object in the hierarchy:
  return obj;
};

Usage

Using the method is simple. As its an extension of the javascript String object you mere chain it from the dot notated sting, like so:

var newObject = {};
'contact.name.first'.toObject(newObject, 'Josey');

Which, if you then log newObject you will get the following:

{
  contact: {
    name: {
      first: 'Josey'
    }
  }
}

Conclusion

I hope this ends up helping someone else; I've found it immensely useful for things like shortcuts to update data via url query strings.