JavaScript How To ...

How to Put a JavaScript Into an HTML Page



The code above will produce this output on an HTML page:

Hello World!

Example Explained

To insert a JavaScript into an HTML page, we use the script tag (also use the type attribute to define the scripting language).

So, the tells where the JavaScript starts and ends:



The word document.write is a standard JavaScript command for writing output to a page.

By entering the document.write command between the tags, the browser will recognize it as a JavaScript command and execute the code line. In this case the browser will write Hello World! to the page:



Note: If we had not entered the script tag, the browser would have treated the document.write("Hello World!") command as pure text, and just write the entire line on the page.

Ending Statements With a Semicolon?

With traditional programming languages, like C++ and Java, each code statement has to end with a semicolon.

Many programmers continue this habit when writing JavaScript, but in general, semicolons are optional! However, semicolons are required if you want to put more than one statement on a single line.

How to Handle Older Browsers

Browsers that do not support JavaScript will display the script as page content. To prevent them from doing this, we may use the HTML comment tag:



The two forward slashes at the end of comment line (//) are a JavaScript comment symbol. This prevents the%