[Deff]

function inpurLimit(a){
		var maxLen = 20;
		if(a.val().length> maxLen){
			aval(a.val().substr(0, maxLen));
		}
		var stringLength=a.val().length;
		if(stringLength<= maxLen){
			a.next('div').first().text(maxLen-stringLength);
		}
	}

$("input").keydown(function() { 
  inpurLimit($(this))
});