Начинающий-Js-кодер,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
div {
border: 2px solid green;
}
</style>
</head>
<body>
<script>
function fn(str)
{
var container = document.createElement("div")
container.appendChild(document.createTextNode(str));
document.body.appendChild(container);
container.style.display = "inline"
var width = container.offsetWidth;
container.style.display = "";
container.style.width = width + "px";
container.style.padding = "0 5px";
}
fn("hello world")
</script>
</body>
</html>