underscore.js#debounce()

gistfile1.js

// @see http://underscorejs.org/underscore.js
// Returns a function, that, as long as it continues to be invoked, will not
// be triggered. The function will be called after it stops being called for
// N milliseconds. If `immediate` is passed, trigger the function on the
// leading edge, instead of the trailing.
_.debounce = function(func, wait, immediate) {
  var timeout;
  return function() {
    var context = this, args = arguments;
    var later = function() {
      timeout = null;
      if (!immediate) func.apply(context, args);
    };
    if (immediate && !timeout) func.apply(context, args);
    clearTimeout(timeout);
    timeout = setTimeout(later, wait);
  };
};