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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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