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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
"use strict";
/**
* From underscore's `_.throttle`
* http://underscorejs.org
* (c) 2009-2014 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
* Underscore may be freely distributed under the MIT license.
*
* Returns a function, that, when invoked, will only be triggered at most once during a
* given window of time. The throttled function will run as much as it can, without ever
* going more than once per wait duration.
*
* @param {Function} func
* The function to throttle
* @param {number} wait
* The wait period
* @param {Object} scope
* The scope to use for func
* @return {Function} The throttled function
*/
function throttle(func, wait, scope) {
let args, result;
let timeout = null;
let previous = 0;
const later = function() {
previous = Date.now();
timeout = null;
result = func.apply(scope, args);
args = null;
};
const throttledFunction = function() {
const now = Date.now();
const remaining = wait - (now - previous);
args = arguments;
if (remaining <= 0) {
clearTimeout(timeout);
timeout = null;
previous = now;
result = func.apply(scope, args);
args = null;
} else if (!timeout) {
timeout = setTimeout(later, remaining);
}
return result;
};
function cancel() {
if (timeout) {
clearTimeout(timeout);
timeout = null;
}
previous = 0;
args = undefined;
result = undefined;
}
function flush() {
if (!timeout) {
return result;
}
previous = 0;
return throttledFunction();
}
throttledFunction.cancel = cancel;
throttledFunction.flush = flush;
return throttledFunction;
}
exports.throttle = throttle;
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