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70 lines
2.6 KiB
JavaScript
70 lines
2.6 KiB
JavaScript
6 years ago
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var debounce = require('./debounce'),
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isObject = require('./isObject');
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/** Error message constants. */
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var FUNC_ERROR_TEXT = 'Expected a function';
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/**
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* Creates a throttled function that only invokes `func` at most once per
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* every `wait` milliseconds. The throttled function comes with a `cancel`
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* method to cancel delayed `func` invocations and a `flush` method to
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* immediately invoke them. Provide `options` to indicate whether `func`
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* should be invoked on the leading and/or trailing edge of the `wait`
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* timeout. The `func` is invoked with the last arguments provided to the
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* throttled function. Subsequent calls to the throttled function return the
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* result of the last `func` invocation.
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*
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* **Note:** If `leading` and `trailing` options are `true`, `func` is
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* invoked on the trailing edge of the timeout only if the throttled function
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* is invoked more than once during the `wait` timeout.
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*
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* If `wait` is `0` and `leading` is `false`, `func` invocation is deferred
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* until to the next tick, similar to `setTimeout` with a timeout of `0`.
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*
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* See [David Corbacho's article](https://css-tricks.com/debouncing-throttling-explained-examples/)
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* for details over the differences between `_.throttle` and `_.debounce`.
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*
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* @static
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* @memberOf _
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* @since 0.1.0
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* @category Function
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* @param {Function} func The function to throttle.
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* @param {number} [wait=0] The number of milliseconds to throttle invocations to.
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* @param {Object} [options={}] The options object.
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* @param {boolean} [options.leading=true]
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* Specify invoking on the leading edge of the timeout.
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* @param {boolean} [options.trailing=true]
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* Specify invoking on the trailing edge of the timeout.
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* @returns {Function} Returns the new throttled function.
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* @example
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*
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* // Avoid excessively updating the position while scrolling.
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* jQuery(window).on('scroll', _.throttle(updatePosition, 100));
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*
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* // Invoke `renewToken` when the click event is fired, but not more than once every 5 minutes.
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* var throttled = _.throttle(renewToken, 300000, { 'trailing': false });
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* jQuery(element).on('click', throttled);
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*
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* // Cancel the trailing throttled invocation.
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* jQuery(window).on('popstate', throttled.cancel);
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*/
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function throttle(func, wait, options) {
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var leading = true,
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trailing = true;
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if (typeof func != 'function') {
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throw new TypeError(FUNC_ERROR_TEXT);
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}
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if (isObject(options)) {
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leading = 'leading' in options ? !!options.leading : leading;
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trailing = 'trailing' in options ? !!options.trailing : trailing;
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}
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return debounce(func, wait, {
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'leading': leading,
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'maxWait': wait,
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'trailing': trailing
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});
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}
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module.exports = throttle;
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