Andrew Zambazos
109 lines
3.4 KiB
JavaScript
109 lines
3.4 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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// Throttler wraps a function and ensures it doesn't get called more than once every `delay` ms.
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// The first fire will always trigger synchronous, and subsequent calls that need to be throttled
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// will happen later asynchronously.
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//
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// Example:
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//
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// let throttler = new Throttler(250, () => { this.refresh() });
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// element.addEventListener("keydown", (event) => { throttler.fire(); });
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//
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// Will ensure `refresh` happens no more than once every 250ms no matter how often `fire` is called:
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//
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// 0ms 250ms 500ms
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// time: |---------------------------|---------------------------|
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// fire: ^ ^ ^ ^ ^ ^ ^ ^
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// refreshes: * (1) * (2) * (3)
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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 Throttler
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{
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constructor(callback, delay)
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{
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console.assert(typeof callback === "function");
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console.assert(delay >= 0);
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this._callback = callback;
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this._delay = delay;
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this._lastArguments = [];
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this._timeoutIdentifier = undefined;
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this._lastFireTime = -this._delay;
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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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fire()
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{
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this._lastArguments = arguments;
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let remaining = this._delay - (Date.now() - this._lastFireTime);
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if (remaining <= 0) {
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this._execute();
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return;
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}
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if (this._timeoutIdentifier)
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return;
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this._timeoutIdentifier = setTimeout(() => {
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this._execute();
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}, remaining);
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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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}
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// Private
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_execute()
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{
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this._lastFireTime = Date.now();
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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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