jQuery.extend

extend.js

jQuery.extend = jQuery.fn.extend = function() {
	var options, name, src, copy, copyIsArray, clone,
		target = arguments[0] || {},
		i = 1,
		length = arguments.length,
		deep = false;

	// Handle a deep copy situation
	if ( typeof target === "boolean" ) {
		deep = target;
		target = arguments[1] || {};
		// skip the boolean and the target
		i = 2;
	}

	// Handle case when target is a string or something (possible in deep copy)
	if ( typeof target !== "object" && !jQuery.isFunction(target) ) {
		target = {};
	}

	// extend jQuery itself if only one argument is passed
	if ( length === i ) {
		target = this;
		--i;
	}

	for ( ; i < length; i++ ) {
		// Only deal with non-null/undefined values
		if ( (options = arguments[ i ]) == null ) continue;
		// Extend the base object
		for ( name in options ) {
			src = target[ name ];
			copy = options[ name ];

			// Prevent never-ending loop
			if ( target === copy ) continue;

			// Recurse if we're merging plain objects or arrays
			if ( deep && copy && ( jQuery.isPlainObject(copy) || (copyIsArray = jQuery.isArray(copy)) ) ) {
				if ( copyIsArray ) {
					copyIsArray = false;
					clone = src && jQuery.isArray(src) ? src : [];

				} else {
					clone = src && jQuery.isPlainObject(src) ? src : {};
				}

				// Never move original objects, clone them
				target[ name ] = jQuery.extend( deep, clone, copy );

			// Don't bring in undefined values
			} else if ( copy !== undefined ) {
				target[ name ] = copy;
			}
		}
	}

	// Return the modified object
	return target;
};