JavaScript/Bookmarklets

Bookmarklets are one line scripts stored in the URL field of a bookmark. Bookmarklets have been around for a long time so they will work in older browsers.

JavaScript URI scheme

You should be familiar with URL that start with schemes like http and ftp, e.g. http://en.wikibooks.org/. There is also the JavaScript scheme, which is used to start every bookmarklet.

JavaScript:alert("Hello, World!");

Using multiple lines of code

Since you cannot have line breaks in bookmarklets you must use a semicolon at the end of each code statement instead.

JavaScript:name=prompt("What is your name?")<font color="red">;</font>alert("Hello, " + name);

The JavaScript Protocol in Links

The JavaScript protocol can be used in links. This may be considered bad practice, as it prevents access for or confuses users who have disabled JavaScript. See Best Practices.

<a href="JavaScript:document.bgColor='#0000FF'">blue background</a>

Examples

A large quantity of links may be found on bookmarklets.com, which show a variety of features that can be performed within JavaScript.