Custom Deep Extend Mixin for Underscore

deepExtend.js

var slice = [].slice;
if (!_.deepExtend) {
	var behavior = {
		"*": function(obj, sourcePropKey, sourcePropVal) {
			obj[sourcePropKey] = sourcePropVal;
		},
		"object": function(obj, sourcePropKey, sourcePropVal) {
			obj[sourcePropKey] = deepExtend(obj[sourcePropKey] || {}, sourcePropVal);
		},
		"array": function(obj, sourcePropKey, sourcePropVal) {
			obj[sourcePropKey] = [];
			_.each(sourcePropVal, function(item, idx) {
				behavior[getHandlerName(item)](obj[sourcePropKey], idx, item);
			}, this);
		}
	},
		getActualType = function(val) {
			if (_.isArray(val)) {
				return "array";
			}
			if (_.isDate(val)) {
				return "date";
			}
			if (_.isRegExp(val)) {
				return "regex";
			}
			return typeof val;
		},
		getHandlerName = function(val) {
			var propType = getActualType(val);
			return behavior[propType] ? propType : "*";
		},
		deepExtend = function(obj) {
			_.each(slice.call(arguments, 1), function(source) {
				_.each(source, function(sourcePropVal, sourcePropKey) {
					behavior[getHandlerName(sourcePropVal)](obj, sourcePropKey, sourcePropVal);
				});
			});
			return obj;
		};

	_.mixin({
		deepExtend: deepExtend
	});
}