Andrew Zambazos
135 lines
4.0 KiB
JavaScript
135 lines
4.0 KiB
JavaScript
/*
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* Copyright (C) 2019 Apple Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
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* THE POSSIBILITY OF SUCH DAMAGE.
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*/
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// Debouncer wraps a function and continues to delay its invocation as long as
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// clients continue to delay its firing. The most recent delay call overrides
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// previous calls. Delays may be timeouts, animation frames, or microtasks.
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//
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// Example:
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//
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// let debouncer = new Debouncer(() => { this.refresh() });
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// element.addEventListener("keydown", (event) => { debouncer.delayForTime(100); });
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//
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// Will ensure `refresh` will not happen until no keyevent has happened in 100ms:
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//
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// 0ms 100ms 200ms 300ms 400ms
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// time: |-------------|-------------|-------------|-------------|
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// delay: ^ ^ ^ ^ ^ ^ ^ ^
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// refreshes: * (1)
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//
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// When the wrapped function is actually called, it will be given the most recent set of arguments.
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class Debouncer
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{
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constructor(callback)
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{
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console.assert(typeof callback === "function");
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this._callback = callback;
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this._lastArguments = [];
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this._timeoutIdentifier = undefined;
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this._animationFrameIdentifier = undefined;
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this._promiseIdentifier = undefined;
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}
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// Public
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force()
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{
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this._lastArguments = arguments;
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this._execute();
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}
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delayForTime(time, ...args)
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{
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console.assert(time >= 0);
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this.cancel();
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this._lastArguments = args;
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this._timeoutIdentifier = setTimeout(() => {
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this._execute();
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}, time);
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}
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delayForFrame()
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{
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this.cancel();
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this._lastArguments = arguments;
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this._animationFrameIdentifier = requestAnimationFrame(() => {
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this._execute();
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});
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}
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delayForMicrotask()
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{
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this.cancel();
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this._lastArguments = arguments;
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let promiseIdentifier = Symbol("next-microtask");
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this._promiseIdentifier = promiseIdentifier;
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queueMicrotask(() => {
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if (this._promiseIdentifier === promiseIdentifier)
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this._execute();
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});
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}
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cancel()
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{
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this._lastArguments = [];
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if (this._timeoutIdentifier) {
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clearTimeout(this._timeoutIdentifier);
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this._timeoutIdentifier = undefined;
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}
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if (this._animationFrameIdentifier) {
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cancelAnimationFrame(this._animationFrameIdentifier);
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this._animationFrameIdentifier = undefined;
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}
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if (this._promiseIdentifier)
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this._promiseIdentifier = undefined;
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}
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// Private
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_execute()
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{
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let args = this._lastArguments;
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this.cancel();
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this._callback.apply(undefined, args);
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}
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}
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