node/tools/eslint/node_modules/lodash/throttle.js

var debounce = require('./debounce'),
    isObject = require('./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 `func` invocations and a `flush` method to
 * immediately invoke them. Provide an options object 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.
 *
 * 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.
 * 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;