60 lines
1.5 KiB
Plaintext
60 lines
1.5 KiB
Plaintext
'use strict';
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const DEBOUNCE_DEFAULTS = {
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trailing: true
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};
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function debounce(fn, wait = 25, options = {}) {
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options = { ...DEBOUNCE_DEFAULTS, ...options };
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if (!Number.isFinite(wait)) {
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throw new TypeError("Expected `wait` to be a finite number");
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}
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let leadingValue;
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let timeout;
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let resolveList = [];
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let currentPromise;
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let trailingArgs;
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const applyFn = (_this, args) => {
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currentPromise = _applyPromised(fn, _this, args);
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currentPromise.finally(() => {
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currentPromise = null;
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if (options.trailing && trailingArgs && !timeout) {
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const promise = applyFn(_this, trailingArgs);
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trailingArgs = null;
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return promise;
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}
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});
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return currentPromise;
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};
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return function(...args) {
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if (currentPromise) {
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if (options.trailing) {
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trailingArgs = args;
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}
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return currentPromise;
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}
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return new Promise((resolve) => {
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const shouldCallNow = !timeout && options.leading;
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clearTimeout(timeout);
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timeout = setTimeout(() => {
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timeout = null;
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const promise = options.leading ? leadingValue : applyFn(this, args);
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for (const _resolve of resolveList) {
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_resolve(promise);
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}
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resolveList = [];
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}, wait);
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if (shouldCallNow) {
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leadingValue = applyFn(this, args);
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resolve(leadingValue);
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} else {
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resolveList.push(resolve);
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}
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});
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};
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}
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async function _applyPromised(fn, _this, args) {
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return await fn.apply(_this, args);
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}
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exports.debounce = debounce;
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