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Inline code versus external files

To externalize the

sayHi()

function into a file named

external.js

, you copy the function text itself

(Figure 5-1).

Figure 5-1

Then the HTML code can be updated to include the external file:

<html>

<head>

<title>Title of Page</title>

</head>

<body>

</body>

</html>

Inline code versus external files

When should you write code inline versus writing the code in an external file? Although no hard

and fast rules exist about when to use either method, the general consensus is that large amounts of

JavaScript should never be included inline for a number of reasons:

Security

— Anyone can see exactly what the code is doing just by viewing the source of the page.

If a malicious developer examines the code, he might find security holes that could compromise

the site or application. Additionally, copyright and other intellectual property notices can be

included in external files without interrupting the flow of the page.

No rules exist about what you can include in a single JavaScript source file, meaning

that you are free to include any number of class definitions, functions, and so on, in

a single file.

external.js

function sayHi() {

alert("Hi");

}

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JavaScript in the Browser

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