Updated angular extend to ignore undefined properties

[martynasb]

Updated angular.extend to ignore undefined properties.

[mary-poppins]

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[petebacondarwin]

@martynasb - can you give a use case where this was a problem for you. It would be great to keep angular.extend as fast as possible and I would like to see what the real world problem was that cause you to add this extra check.

[martynasb]

@petebacondarwin Sure. I was working on a project that involves map visualizations. A map has certain settings: width, height, tile provider, etc.

A developer has an option of setting these options himself to override the defaults.

For example:

We get the default settings:
var defaultSettings = mapSettingsService.getDefaultSettings();

Then get the user options:

//
var userSettings = {
width: attrs.mapWidth,
height: attrs.mapHeight,
tiles: attrs.tiles, /* i.e. google */
...
};

Merge them:
var mapSettings = $.extend(true, {}, defaultSettings, userSettings);

I had to use jQuery's $.extend() because ignores undefined values.
I would prefer doing this with angular.extend

I hope this makes sense