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63 lines
2.4 KiB
JavaScript
63 lines
2.4 KiB
JavaScript
var debounce = require('./debounce'),
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isObject = require('../lang/isObject');
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/** Used as the `TypeError` message for "Functions" methods. */
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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 invocations. Provide an options object to indicate
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* that `func` should be invoked on the leading and/or trailing edge of the
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* `wait` timeout. Subsequent calls to the throttled function return the
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* result of the last `func` call.
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*
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* **Note:** If `leading` and `trailing` options are `true`, `func` is invoked
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* on the trailing edge of the timeout only if the the throttled function is
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* invoked more than once during the `wait` timeout.
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*
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* See [David Corbacho's article](http://drupalmotion.com/article/debounce-and-throttle-visual-explanation)
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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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* @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] Specify invoking on the leading
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* edge of the timeout.
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* @param {boolean} [options.trailing=true] Specify invoking on the trailing
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* 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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* jQuery('.interactive').on('click', _.throttle(renewToken, 300000, {
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* 'trailing': false
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* }));
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*
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* // cancel a trailing throttled call
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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 (options === false) {
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leading = false;
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} else 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, { 'leading': leading, 'maxWait': +wait, 'trailing': trailing });
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}
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module.exports = throttle;
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