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var debounce = require('./debounce'),
isObject = require('./isObject');
/** Error message constants. */
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 `func` invocations and a `flush` method to
* immediately invoke them. Provide `options` to indicate whether `func`
* should be invoked on the leading and/or trailing edge of the `wait`
* timeout. The `func` is invoked with the last arguments provided to the
* throttled function. Subsequent calls to the throttled function return the
* result of the last `func` invocation.
*
* **Note:** If `leading` and `trailing` options are `true`, `func` is
* invoked on the trailing edge of the timeout only if the throttled function
* is invoked more than once during the `wait` timeout.
*
* If `wait` is `0` and `leading` is `false`, `func` invocation is deferred
* until to the next tick, similar to `setTimeout` with a timeout of `0`.
*
* See [David Corbacho's article](https://css-tricks.com/debouncing-throttling-explained-examples/)
* for details over the differences between `_.throttle` and `_.debounce`.
*
* @static
* @memberOf _
* @since 0.1.0
* @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.
* var throttled = _.throttle(renewToken, 300000, { 'trailing': false });
* jQuery(element).on('click', throttled);
*
* // Cancel the trailing throttled invocation.
* 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 (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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