<!DOCTYPE html>
<html>
<body>
<div style="background:red;" id="myDiv">This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text.</div><br>
<button type="button" onclick="myFunction()">Set max width</button>
<script>
function myFunction() {
document.getElementById("myDiv").style.maxWidth = "100px";
}
</script>
</body>
</html>