一，效果图。
二，代码。
<!DOCTYPE html>
<html> <head> <meta charset="utf-8"> <title>javascript 语法</title> </head> <body> <!--JavaScript 字面量--> <p id="demo"></p> <script> document.getElementById("demo").innerHTML = 123e5; document.getElementById("demo").innerHTML = "John doe"; document.getElementById("demo").innerHTML = 5 * 10; var length; length = 6; document.getElementById("demo").innerHTML = length; document.getElementById("demo").innerHTML = (5 + 6) * 10; </script> </body> </html>