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Tip of the Day
Language: Web
Expertise: Beginner
Nov 14, 1998



Building the Right Environment to Support AI, Machine Learning and Deep Learning

Preventing Undefined JavaScript Function Errors

You can define JavaScript functions anywhere in an HTML file, however, the best place to define them is in the HTML header (between the <HEAD> and </HEAD> tags). If a JavaScript function is defined in the body of the document and it doesn't write out elements of the page layout, it's possible for the function to be invoked before it is fully defined, causing obscure JavaScript errors. For instance, say you have a function rollover() that swaps images on a user mouse-over. If the user is moving the mouse over that image while the browser is still reading the remainder of the HTML file and hasn't finishing adding the rollover function to its function list, an error might result. FrontPage 97 sometimes puts JavaScript functions in the body of an HTML document when using the WebBot feature. By placing JavaScript functions in the HTML header, you can ensure that these errors do not occur.
Erik Goetze
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