When learning a new language, everyone likes to use "hello world" as the first program, so now we write a JavaScript version:
<html> <head></head> <body> <script> alert("hello world!"); </script> </body> </html>
The JavaScript code is placed in <script> ...</script> tag, the effect of this code is to pop up a small box that displays "hello world!". Save this code as an HTML file, name it "test.html", then double-click the file, the system will call the FireFox browser to open it:
Visible writing JavaScript program It is very convenient.