141 lines
5.4 KiB
JavaScript
141 lines
5.4 KiB
JavaScript
/* eslint-disable no-undefined,no-param-reassign,no-shadow */
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/**
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* Throttle execution of a function. Especially useful for rate limiting
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* execution of handlers on events like resize and scroll.
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*
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* @param {number} delay - A zero-or-greater delay in milliseconds. For event callbacks, values around 100 or 250 (or even higher) are most useful.
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* @param {boolean} [noTrailing] - Optional, defaults to false. If noTrailing is true, callback will only execute every `delay` milliseconds while the
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* throttled-function is being called. If noTrailing is false or unspecified, callback will be executed one final time
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* after the last throttled-function call. (After the throttled-function has not been called for `delay` milliseconds,
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* the internal counter is reset).
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* @param {Function} callback - A function to be executed after delay milliseconds. The `this` context and all arguments are passed through, as-is,
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* to `callback` when the throttled-function is executed.
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* @param {boolean} [debounceMode] - If `debounceMode` is true (at begin), schedule `clear` to execute after `delay` ms. If `debounceMode` is false (at end),
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* schedule `callback` to execute after `delay` ms.
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*
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* @returns {Function} A new, throttled, function.
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*/
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function throttle (delay, noTrailing, callback, debounceMode) {
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/*
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* After wrapper has stopped being called, this timeout ensures that
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* `callback` is executed at the proper times in `throttle` and `end`
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* debounce modes.
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*/
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var timeoutID;
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var cancelled = false; // Keep track of the last time `callback` was executed.
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var lastExec = 0; // Function to clear existing timeout
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function clearExistingTimeout() {
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if (timeoutID) {
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clearTimeout(timeoutID);
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}
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} // Function to cancel next exec
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function cancel() {
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clearExistingTimeout();
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cancelled = true;
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} // `noTrailing` defaults to falsy.
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if (typeof noTrailing !== 'boolean') {
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debounceMode = callback;
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callback = noTrailing;
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noTrailing = undefined;
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}
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/*
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* The `wrapper` function encapsulates all of the throttling / debouncing
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* functionality and when executed will limit the rate at which `callback`
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* is executed.
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*/
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function wrapper() {
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for (var _len = arguments.length, arguments_ = new Array(_len), _key = 0; _key < _len; _key++) {
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arguments_[_key] = arguments[_key];
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}
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var self = this;
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var elapsed = Date.now() - lastExec;
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if (cancelled) {
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return;
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} // Execute `callback` and update the `lastExec` timestamp.
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function exec() {
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lastExec = Date.now();
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callback.apply(self, arguments_);
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}
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/*
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* If `debounceMode` is true (at begin) this is used to clear the flag
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* to allow future `callback` executions.
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*/
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function clear() {
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timeoutID = undefined;
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}
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if (debounceMode && !timeoutID) {
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/*
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* Since `wrapper` is being called for the first time and
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* `debounceMode` is true (at begin), execute `callback`.
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*/
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exec();
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}
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clearExistingTimeout();
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if (debounceMode === undefined && elapsed > delay) {
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/*
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* In throttle mode, if `delay` time has been exceeded, execute
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* `callback`.
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*/
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exec();
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} else if (noTrailing !== true) {
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/*
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* In trailing throttle mode, since `delay` time has not been
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* exceeded, schedule `callback` to execute `delay` ms after most
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* recent execution.
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*
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* If `debounceMode` is true (at begin), schedule `clear` to execute
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* after `delay` ms.
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*
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* If `debounceMode` is false (at end), schedule `callback` to
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* execute after `delay` ms.
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*/
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timeoutID = setTimeout(debounceMode ? clear : exec, debounceMode === undefined ? delay - elapsed : delay);
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}
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}
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wrapper.cancel = cancel; // Return the wrapper function.
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return wrapper;
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}
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/* eslint-disable no-undefined */
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/**
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* Debounce execution of a function. Debouncing, unlike throttling,
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* guarantees that a function is only executed a single time, either at the
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* very beginning of a series of calls, or at the very end.
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*
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* @param {number} delay - A zero-or-greater delay in milliseconds. For event callbacks, values around 100 or 250 (or even higher) are most useful.
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* @param {boolean} [atBegin] - Optional, defaults to false. If atBegin is false or unspecified, callback will only be executed `delay` milliseconds
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* after the last debounced-function call. If atBegin is true, callback will be executed only at the first debounced-function call.
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* (After the throttled-function has not been called for `delay` milliseconds, the internal counter is reset).
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* @param {Function} callback - A function to be executed after delay milliseconds. The `this` context and all arguments are passed through, as-is,
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* to `callback` when the debounced-function is executed.
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*
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* @returns {Function} A new, debounced function.
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*/
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function debounce (delay, atBegin, callback) {
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return callback === undefined ? throttle(delay, atBegin, false) : throttle(delay, callback, atBegin !== false);
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}
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export { debounce, throttle };
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//# sourceMappingURL=index.esm.js.map
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