Function extend

vue.js:344–349

(to, _from)

     ***********************************************************************************************/
    //对象浅拷贝，参数（to, _from）循环_from的值，会覆盖掉to的值
    function extend(to, _from) {
        for (var key in _from) {
            to[key] = _from[key];
        }
        return to
    }

    /**
     * Merge an Array of Objects into a single Object.