This simple jQuery function can be used to trigger a callback everytime user stops typing. Just apply this to any text input fields such as textarea to see it in action.

(function($) {
$.fn.donetyping = function(callback){
    var _this = $(this);
    var x_timer;    
    _this.keyup(function (){
        clearTimeout(x_timer);
        x_timer = setTimeout(clear_timer, 1000);
    }); 

    function clear_timer(){
        clearTimeout(x_timer);
        callback.call(_this);
    }
}
})(jQuery);

Usage :

$('textarea').donetyping(function(callback){
        //your code goes here.
});