119 lines
3.8 KiB
HTML
119 lines
3.8 KiB
HTML
<!--
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@license
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Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
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This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
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The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
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The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
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Code distributed by Google as part of the polymer project is also
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subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
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-->
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<link rel="import" href="boot.html">
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<link rel="import" href="mixin.html">
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<link rel="import" href="async.html">
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<script>
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(function() {
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'use strict';
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/**
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* @summary Collapse multiple callbacks into one invocation after a timer.
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* @memberof Polymer
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*/
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class Debouncer {
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constructor() {
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this._asyncModule = null;
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this._callback = null;
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this._timer = null;
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}
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/**
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* Sets the scheduler; that is, a module with the Async interface,
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* a callback and optional arguments to be passed to the run function
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* from the async module.
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*
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* @param {!AsyncInterface} asyncModule Object with Async interface.
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* @param {function()} callback Callback to run.
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* @return {void}
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*/
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setConfig(asyncModule, callback) {
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this._asyncModule = asyncModule;
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this._callback = callback;
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this._timer = this._asyncModule.run(() => {
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this._timer = null;
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this._callback();
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});
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}
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/**
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* Cancels an active debouncer and returns a reference to itself.
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*
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* @return {void}
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*/
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cancel() {
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if (this.isActive()) {
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this._asyncModule.cancel(this._timer);
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this._timer = null;
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}
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}
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/**
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* Flushes an active debouncer and returns a reference to itself.
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*
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* @return {void}
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*/
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flush() {
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if (this.isActive()) {
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this.cancel();
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this._callback();
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}
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}
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/**
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* Returns true if the debouncer is active.
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*
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* @return {boolean} True if active.
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*/
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isActive() {
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return this._timer != null;
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}
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/**
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* Creates a debouncer if no debouncer is passed as a parameter
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* or it cancels an active debouncer otherwise. The following
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* example shows how a debouncer can be called multiple times within a
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* microtask and "debounced" such that the provided callback function is
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* called once. Add this method to a custom element:
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*
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* _debounceWork() {
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* this._debounceJob = Polymer.Debouncer.debounce(this._debounceJob,
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* Polymer.Async.microTask, () => {
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* this._doWork();
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* });
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* }
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*
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* If the `_debounceWork` method is called multiple times within the same
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* microtask, the `_doWork` function will be called only once at the next
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* microtask checkpoint.
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*
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* Note: In testing it is often convenient to avoid asynchrony. To accomplish
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* this with a debouncer, you can use `Polymer.enqueueDebouncer` and
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* `Polymer.flush`. For example, extend the above example by adding
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* `Polymer.enqueueDebouncer(this._debounceJob)` at the end of the
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* `_debounceWork` method. Then in a test, call `Polymer.flush` to ensure
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* the debouncer has completed.
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*
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* @param {Debouncer?} debouncer Debouncer object.
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* @param {!AsyncInterface} asyncModule Object with Async interface
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* @param {function()} callback Callback to run.
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* @return {!Debouncer} Returns a debouncer object.
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*/
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static debounce(debouncer, asyncModule, callback) {
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if (debouncer instanceof Debouncer) {
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debouncer.cancel();
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} else {
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debouncer = new Debouncer();
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}
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debouncer.setConfig(asyncModule, callback);
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return debouncer;
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}
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}
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Polymer.Debouncer = Debouncer;
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})();
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</script>
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