copy.js #1

"use strict";

var aFrom  = require("../array/from")
  , assign = require("./assign")
  , value  = require("./valid-value");

module.exports = function (obj/*, propertyNames, options*/) {
	var copy = Object(value(obj)), propertyNames = arguments[1], options = Object(arguments[2]);
	if (copy !== obj && !propertyNames) return copy;
	var result = {};
	if (propertyNames) {
		aFrom(propertyNames, function (propertyName) {
			if (options.ensure || propertyName in obj) result[propertyName] = obj[propertyName];
		});
	} else {
		assign(result, obj);
	}
	return result;
};