要设置字体大小，请使用JavaScript中的fontSize属性。您可以尝试运行以下代码以使用JavaScript设置文本的字体大小-
<!DOCTYPE html>
<html>
<body>
<h1>Heading 1</h1>
<p id = "myID">
This is Demo Text. This is Demo Text. This is Demo Text. This is Demo Text.
This is Demo Text. This is Demo Text. This is Demo Text. This is Demo Text.
</p>
<button type = "button" onclick = "display()">Set Font Family and Size</button>
<script>
function display() {
document.getElementById("myID").style.fontFamily = "verdana,sans-serif";
document.getElementById("myID").style.fontSize = "smaller";
}
</script>
</body>
</html>