_.debounce
_.debounce = function(func, wait, immediate) {
var result;
var timeout = null;
return function() {
var context = this, args = arguments;
var later = function() {
timeout = null;
if (!immediate) result = func.apply(context, args);
};
var callNow = immediate && !timeout;
clearTimeout(timeout);
timeout = setTimeout(later, wait);
if (callNow) result = func.apply(context, args);
return result;
};
};