1  var debounce = require('./debounce'),
 2      isObject = require('./isObject');
 3  
 4  /** Error message constants. */
 5  var FUNC_ERROR_TEXT = 'Expected a function';
 6  
 7  /**
 8   * Creates a throttled function that only invokes `func` at most once per
 9   * every `wait` milliseconds. The throttled function comes with a `cancel`
10   * method to cancel delayed `func` invocations and a `flush` method to
11   * immediately invoke them. Provide `options` to indicate whether `func`
12   * should be invoked on the leading and/or trailing edge of the `wait`
13   * timeout. The `func` is invoked with the last arguments provided to the
14   * throttled function. Subsequent calls to the throttled function return the
15   * result of the last `func` invocation.
16   *
17   * **Note:** If `leading` and `trailing` options are `true`, `func` is
18   * invoked on the trailing edge of the timeout only if the throttled function
19   * is invoked more than once during the `wait` timeout.
20   *
21   * If `wait` is `0` and `leading` is `false`, `func` invocation is deferred
22   * until to the next tick, similar to `setTimeout` with a timeout of `0`.
23   *
24   * See [David Corbacho's article](https://css-tricks.com/debouncing-throttling-explained-examples/)
25   * for details over the differences between `_.throttle` and `_.debounce`.
26   *
27   * @static
28   * @memberOf _
29   * @since 0.1.0
30   * @category Function
31   * @param {Function} func The function to throttle.
32   * @param {number} [wait=0] The number of milliseconds to throttle invocations to.
33   * @param {Object} [options={}] The options object.
34   * @param {boolean} [options.leading=true]
35   *  Specify invoking on the leading edge of the timeout.
36   * @param {boolean} [options.trailing=true]
37   *  Specify invoking on the trailing edge of the timeout.
38   * @returns {Function} Returns the new throttled function.
39   * @example
40   *
41   * // Avoid excessively updating the position while scrolling.
42   * jQuery(window).on('scroll', _.throttle(updatePosition, 100));
43   *
44   * // Invoke `renewToken` when the click event is fired, but not more than once every 5 minutes.
45   * var throttled = _.throttle(renewToken, 300000, { 'trailing': false });
46   * jQuery(element).on('click', throttled);
47   *
48   * // Cancel the trailing throttled invocation.
49   * jQuery(window).on('popstate', throttled.cancel);
50   */
51  function throttle(func, wait, options) {
52    var leading = true,
53        trailing = true;
54  
55    if (typeof func != 'function') {
56      throw new TypeError(FUNC_ERROR_TEXT);
57    }
58    if (isObject(options)) {
59      leading = 'leading' in options ? !!options.leading : leading;
60      trailing = 'trailing' in options ? !!options.trailing : trailing;
61    }
62    return debounce(func, wait, {
63      'leading': leading,
64      'maxWait': wait,
65      'trailing': trailing
66    });
67  }
68  
69  module.exports = throttle;