Function debounce

underscore.js:1179–1211

(func, wait, immediate)

  // parameter. If `immediate` is passed, the argument function will be
  // triggered at the beginning of the sequence instead of at the end.
  function debounce(func, wait, immediate) {
    var timeout, previous, args, result, context;

    var later = function() {
      var passed = now() - previous;
      if (wait > passed) {
        timeout = setTimeout(later, wait - passed);
      } else {
        timeout = null;
        if (!immediate) result = func.apply(context, args);
        // This check is needed because `func` can recursively invoke `debounced`.
        if (!timeout) args = context = null;
      }
    };

    var debounced = restArguments(function(_args) {
      context = this;
      args = _args;
      previous = now();
      if (!timeout) {
        timeout = setTimeout(later, wait);
        if (immediate) result = func.apply(context, args);
      }
      return result;
    });

    debounced.cancel = function() {
      clearTimeout(timeout);
      timeout = args = context = null;
    };

    return debounced;
  }

  // Returns the first function passed as an argument to the second,
  // allowing you to adjust arguments, run code before and after, and