soft-extend/index.js

Non-destructive extend. Just appends new properties to an object, keeping old ones.

/**
 * Append all not-existing props to the initial object
 *
 * @return {[type]} [description]
 */
module.exports = function softExtend(){
	var args = [].slice.call(arguments);
	var res = args[0];
	var l = args.length;

	if (typeof res !== 'object') throw Error('Bad argument');

	for (var i = 1, l = args.length, obj; i < l; i++) {
		obj = args[i];
		if (typeof obj === 'object') {
			for (var prop in obj) {
				if (res[prop] === undefined) {
					res[prop] = obj[prop];
				}
				else if (typeof res[prop] === 'object') {
					softExtend(res[prop], obj[prop])
				}
			}
		}
	}

	return res;
};