Javascrit .createTextNode output is giving errors

I created a website where it tells you your age. I use document.createTextNode to store the output but the output is not working properly. Here is the output code

var h1 = document.createElement("p");
h1.setAttribute("id", "mainText")
var mainText = document.createTextNode("You are ", ageYears, " years, ", ageMonths, " 
months and ", ageDays, " days old.");
h1.appendChild(mainText);
document.getElementById("new-age").appendChild(h1);

When I run my code, it only outputs the first part, “You are”. Is there any way to output the entire message.