Function optimize

vue.js:14301–14316

* Goal of the optimizer: walk the generated template AST tree * and detect sub-trees that are purely static, i.e. parts of * the DOM that never needs to change. * * Once we detect these sub-trees, we can: * * 1. Hoist them into constants, so that we no longer need to

(root, options)

     *  根据node.static或者 node.once 标记staticRoot的状态
     */
    function optimize(root, options) {
        if (!root) {
            return
        }
        //匹配type,tag,attrsList,attrsMap,plain,parent,children,attrs + staticKeys 字符串
        isStaticKey = genStaticKeysCached(options.staticKeys || '');
        //保留标签 判断是不是真的是 html 原有的标签 或者svg标签
        isPlatformReservedTag = options.isReservedTag || no;
        // first pass: mark all non-static nodes.
        ////第一遍:标记所有非静态节点。
        //循环递归虚拟node，标记不是静态节点
        markStatic$1(root);
        // second pass: mark static roots.
        //第二步:标记静态根。
        markStaticRoots(root, false);
    }

    //匹配type,tag,attrsList,attrsMap,plain,parent,children,attrs +key 字符串
    function genStaticKeys$1(keys) {