Function mergeData

vue.js:1717–1735

* Helper that recursively merges two data objects together. * 递归合并数据 深度拷贝

(to, from)

     * 递归合并数据 深度拷贝
     */
    function mergeData(to, from) {
        if (!from) {
            return to
        }
        var key, toVal, fromVal;
        var keys = Object.keys(from); //获取对象的keys 变成数组
        for (var i = 0; i < keys.length; i++) {
            key = keys[i]; //获取对象的key
            toVal = to[key]; //
            fromVal = from[key]; //获取对象的值
            if (!hasOwn(to, key)) { //如果from对象的key在to对象中没有
                set(to, key, fromVal);
            } else if (isPlainObject(toVal) && isPlainObject(fromVal)) {
                //深层递归
                mergeData(toVal, fromVal);
            }
        }
        return to
    }

    /**
     * Data