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var debounce = require('./debounce'),
isObject = require('../lang/isObject');
/** Used as the `TypeError` message for "Functions" methods. */
var FUNC_ERROR_TEXT = 'Expected a function';
/**
* Creates a throttled function that only invokes `func` at most once per
* every `wait` milliseconds. The throttled function comes with a `cancel`
* method to cancel delayed invocations. Provide an options object to indicate
* that `func` should be invoked on the leading and/or trailing edge of the
* `wait` timeout. Subsequent calls to the throttled function return the
* result of the last `func` call.
*
* **Note:** If `leading` and `trailing` options are `true`, `func` is invoked
* on the trailing edge of the timeout only if the the throttled function is
* invoked more than once during the `wait` timeout.
*
* See [David Corbacho's article](http://drupalmotion.com/article/debounce-and-throttle-visual-explanation)
* for details over the differences between `_.throttle` and `_.debounce`.
*
* @static
* @memberOf _
* @category Function
* @param {Function} func The function to throttle.
* @param {number} [wait=0] The number of milliseconds to throttle invocations to.
* @param {Object} [options] The options object.
* @param {boolean} [options.leading=true] Specify invoking on the leading
* edge of the timeout.
* @param {boolean} [options.trailing=true] Specify invoking on the trailing
* edge of the timeout.
* @returns {Function} Returns the new throttled function.
* @example
*
* // avoid excessively updating the position while scrolling
* jQuery(window).on('scroll', _.throttle(updatePosition, 100));
*
* // invoke `renewToken` when the click event is fired, but not more than once every 5 minutes
* jQuery('.interactive').on('click', _.throttle(renewToken, 300000, {
* 'trailing': false
* }));
*
* // cancel a trailing throttled call
* jQuery(window).on('popstate', throttled.cancel);
*/
function throttle(func, wait, options) {
var leading = true,
trailing = true;
if (typeof func != 'function') {
throw new TypeError(FUNC_ERROR_TEXT);
}
if (options === false) {
leading = false;
} else if (isObject(options)) {
leading = 'leading' in options ? !!options.leading : leading;
trailing = 'trailing' in options ? !!options.trailing : trailing;
}
return debounce(func, wait, { 'leading': leading, 'maxWait': +wait, 'trailing': trailing });
}
module.exports = throttle;
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