56 lines
1.6 KiB
JavaScript
56 lines
1.6 KiB
JavaScript
// Taken from underscore.js (slightly modified to add the getNow function and use const/let over var)
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// https://github.com/jashkenas/underscore/blob/master/underscore.js#L830-L874
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// Returns a function, that, when invoked, will only be triggered at most once
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// during a given window of time. Normally, the throttled function will run
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// as much as it can, without ever going more than once per `wait` duration;
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// but if you'd like to disable the execution on the leading edge, pass
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// `{leading: false}`. To disable execution on the trailing edge, ditto.
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export default function throttle(func, wait, options) {
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let timeout, context, args, result;
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let previous = 0;
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const getNow = () => new Date().getTime();
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if (!options) options = {};
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const later = function() {
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previous = options.leading === false ? 0 : getNow();
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timeout = null;
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result = func.apply(context, args);
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if (!timeout) context = args = null;
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};
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const throttled = function() {
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const now = getNow();
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if (!previous && options.leading === false) previous = now;
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const remaining = wait - (now - previous);
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context = this;
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args = arguments;
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if (remaining <= 0 || remaining > wait) {
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if (timeout) {
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clearTimeout(timeout);
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timeout = null;
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}
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previous = now;
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result = func.apply(context, args);
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if (!timeout) context = args = null;
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} else if (!timeout && options.trailing !== false) {
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timeout = setTimeout(later, remaining);
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}
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return result;
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};
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throttled.cancel = function() {
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clearTimeout(timeout);
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previous = 0;
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timeout = context = args = null;
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};
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return throttled;
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}
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