highcharts-merge

/**
 * @license Highcharts Merge
 *
 * (c) 2009-2014 Torstein Honsi
 *
 * License: MIT
 *
 * This function is part of the Highcharts core, and shared under an MIT license on
 * user request.
 */

/**
 * Deep merge two or more objects and return a third object. If the first argument is
 * true, the contents of the second object is copied into the first object.
 * Previously this function redirected to jQuery.extend(true), but this had two limitations.
 * First, it deep merged arrays, which lead to workarounds in Highcharts. Second,
 * it copied properties from extended prototypes. 
 */
function merge() {
	var i,
		args = arguments,
		len,
		ret = {},
		doCopy = function (copy, original) {
			var value, key;

			// An object is replacing a primitive
			if (typeof copy !== 'object') {
				copy = {};
			}

			for (key in original) {
				if (original.hasOwnProperty(key)) {
					value = original[key];

					// Copy the contents of objects, but not arrays or DOM nodes
					if (value && typeof value === 'object' && Object.prototype.toString.call(value) !== '[object Array]'
							&& key !== 'renderTo' && typeof value.nodeType !== 'number') {
						copy[key] = doCopy(copy[key] || {}, value);
				
					// Primitives and arrays are copied over directly
					} else {
						copy[key] = original[key];
					}
				}
			}
			return copy;
		};

	// If first argument is true, copy into the existing object. Used in setOptions.
	if (args[0] === true) {
		ret = args[1];
		args = Array.prototype.slice.call(args, 2);
	}

	// For each argument, extend the return
	len = args.length;
	for (i = 0; i < len; i++) {
		ret = doCopy(ret, args[i]);
	}

	return ret;
}