e711257fa2
Utility wrapper for tracking Polymer element properties updates.
Usage example:
``` js
Gerrit.install(plugin => {
plugin.getDomHook('change-view').onAttached(element => {
if (!element.content) { return; }
plugin.attributeHelper(element.content)
.get('change')
.then(change => {
// Is executed once on switching to change view.
});
});
plugin.getDomHook('reply-text').onAttached(element => {
if (!element.content) { return; }
plugin.attributeHelper(element.content)
.bind('text', replyText => {
// Is called every time reply text changes.
});
});
});
```
Change-Id: Ia95364df58489f71ea1fd591a160b73ac1d60e96
88 lines
2.7 KiB
JavaScript
88 lines
2.7 KiB
JavaScript
// Copyright (C) 2017 The Android Open Source Project
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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(function(window) {
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'use strict';
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function GrAttributeHelper(element) {
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this.element = element;
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this._promises = {};
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}
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GrAttributeHelper.prototype._getChangedEventName = function(name) {
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return name.replace(/([a-z])([A-Z])/g, '$1-$2').toLowerCase() + '-changed';
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};
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/**
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* Returns true if the property is defined on wrapped element.
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* @param {string} name
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* @return {boolean}
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*/
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GrAttributeHelper.prototype._elementHasProperty = function(name) {
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return this.element[name] !== undefined;
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};
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GrAttributeHelper.prototype._reportValue = function(callback, value) {
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try {
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callback(value);
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} catch (e) {
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console.info(e);
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}
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};
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/**
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* Binds callback to property updates.
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*
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* @param {string} name Property name.
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* @param {function(?)} callback
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* @return {function()} Unbind function.
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*/
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GrAttributeHelper.prototype.bind = function(name, callback) {
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const attributeChangedEventName = this._getChangedEventName(name);
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const changedHandler = e => this._reportValue(callback, e.detail.value);
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const unbind = () => this.element.removeEventListener(
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attributeChangedEventName, changedHandler);
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this.element.addEventListener(
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attributeChangedEventName, changedHandler);
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if (this._elementHasProperty(name)) {
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this._reportValue(callback, this.element[name]);
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}
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return unbind;
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};
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/**
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* Get value of the property from wrapped object. Waits for the property
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* to be initialized if it isn't defined.
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*
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* @param {string} name Property name.
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* @return {!Promise<?>}
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*/
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GrAttributeHelper.prototype.get = function(name) {
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if (this._elementHasProperty(name)) {
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return Promise.resolve(this.element[name]);
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}
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if (!this._promises[name]) {
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let resolve;
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const promise = new Promise(r => resolve = r);
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const unbind = this.bind(name, value => {
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resolve(value);
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unbind();
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});
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this._promises[name] = promise;
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}
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return this._promises[name];
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};
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window.GrAttributeHelper = GrAttributeHelper;
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})(window);
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