To document.getElementById('x').style.height+14

To document.getElementById('x').style.height+14

css
#x{height:100px;}
js
document.getElementById('x').onkeydown=function(){ if(event.keyCode ==
13){ var h = Number(this.style.height);this.style.height = h+14+'px'; }};
document.getElementById('x').style.height+14 ¢¸ What should I do?
help me