marko-widgets/taglib/preserve-tag.js

Module to support binding of behavior to rendered UI components rendered on the server or client

/*
 * Copyright 2011 eBay Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

var widgets = require('../');

module.exports = function render(input, out) {

    var global = out.global;

    if (global.__rerender === true) {
        var id = input.id;

        // See if the DOM node with the given ID already exists.
        // If so, then reuse the existing DOM node instead of re-rendering
        // the children. We have to put a placeholder node that will get
        // replaced out if we find that the DOM node has already been rendered
        var condition = input['if'];
        if (condition !== false) {
            var existingEl = document.getElementById(id);
            if (existingEl) {
                var widgetsContext = widgets.getWidgetsContext(out);
                var bodyOnly = input.bodyOnly === true;
                // Don't actually render anything since the element is already in the DOM,
                // but keep track that the node is being preserved so that we can ignore
                // it while transforming the old DOM

                if (!bodyOnly) {
                    var tagName = existingEl.tagName;
                    // If we are preserving the entire DOM node (not just the body)
                    // then that means that we have need to render a placeholder to
                    // mark the target location. We can then replace the placeholder
                    // node with the existing DOM node
                    out.write('<' + tagName + ' id="' + id + '"></' + tagName + '>');
                }

                widgetsContext.globalWidgetsContext.addPreservedDOMNode(existingEl, bodyOnly);
                return;
            }
        }
    }

    if (input.renderBody) {
        input.renderBody(out);
    }
};