The JavaScript FAQ
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Javascript FAQ - Table of Contents

Javascript General Questions

• Why this FAQ?
• What is JavaScript?
• What can JavaScript programs do?
• What can't JavaScript programs do?
• What browsers support JavaScript?
• What JavaScript versions are there?
• Where can I get JavaScript documentation?
• How do I print JavaScript output?
• How do I insert comments in JavaScript code?
• How do I hide JS code from old browsers that do not support JavaScript?
• If the user's browser cannot execute JS code, can I display a warning for the user?
• Can I include JavaScript code from external JS files, rather than embedding all my scripts within HTML pages?
• What reserved words are there in JavaScript?

Javascript Navigation Enhancement

• How do I code a select menu with hyperlinks to different pages?
• Can I make a button on my page work as a hyperlink to another page?
• Can I make a button on my page work as the browser's Back button?
• Can I make a button on my page work as the browser's Forward button?
• Can my script access the query string in the current URL?
• Can I pass parameters from one page to another?
• How do I search for a particular text string on the page?

JavaScript Numbers

• What types of numbers can I use in JavaScript code?
• How do I handle mathematical constants in JavaScript?
• Is there a way to use octal and hexadecimal values in JavaScript?
• How do I convert numbers to strings?
• How do I convert strings to numbers?
• How do I convert a number to a different base?
• Is there a way to test whether a particular variable holds a number or a string?
• What arithmetic operations are supported in JavaScript?
• What mathematical functions are supported in JavaScript?
• How do I generate random numbers?
• How can I round a number to n decimal places?
• Sometimes JavaScript computations seem to yield "inaccurate" results, e.g. 0.362*100=36.199999999999996. How can I avoid this?

Javascript Strings

• How do I insert quotes in strings?
• How do I extract substrings from strings?
• How do I convert strings to URL-encoding?
• How do I convert strings from URL-encoding?
• How do I convert numbers to strings?
• How do I convert strings to numbers?
• How do I convert a number to a string representing that number in a non-decimal number system?
• Is there a way to test whether a particular variable holds a number or a string?
• See also Searching for text

Javascript Dialogs

• How do I generate an alert message from JavaScript?
• How do I generate an OK/Cancel dialog box from JavaScript?
• How do I generate a user prompt from JavaScript?
• What value does prompt() return if the user clicked the Cancel button?
• How do I invoke the browser's Find dialog from JavaScript?
• How do I invoke the browser's Add Favorite dialog?

JavaScript Windows

• How do I open a new browser window?
• How do I close a window?
• How do I resize a window?
• How do I maximize a window?
• How do I write script-generated content to another window?
• How do I test whether my other window is still open?
• How do I change another window's title, that is, the content of title bar at the top of the window?

Javascript Frames

• Is my page framed (loaded in a frameset) or is it in the browser's top-level window?
• Bad boys from another website load my page into their frameset. How can I break out of the frameset?
• Can I update two (or more) frames at a time?
• See also External files within layers.

Javascript Forms

• How do I validate the form input before sending it to the server?
• Can I save space in my form by getting more than one input value from just one field?
• Will my form be submitted when the user presses the Enter key?
• How do I disable a radio button (making it not selectable)?

Javascript Layers

• Can I display an external HTML file as part of my page?
• How do I create a new layer from JavaScript?
• How do I delete a layer using JavaScript?

Javascript Images

• How do I change an image when the user's mouse points at it?
• How do I change an image when the user clicks on it?
• Can I create "pressable" buttons with images?

Javascript Mouse Events

• What event properties can I use to analyze mouse events?
• How do I check whether the user clicked the left or right mouse button?
• Can I disable the Windows context menu that normally shows up when the user clicks the right mouse button?
• Can I disable the right-click menu for a particular image, while enabling the normal right-click menu for all other parts of my page?
• How do I detect mouse events with Ctrl, Alt, and Shift keys?
• Can I disable the default browser response for Shift-click?
• See also OnMouseOver and OnMouseDown

Javascript Colors

• How do I change the document's background color?
• How do I change the document's text color and link colors?
• How do I convert RGB values of a color to a hexadecimal string?
• How do I convert a hex color string (e.g. "FFFFCC") to numeric RGB values of the same color?
• What color names are supported by JavaScript?

Javascript File Access

• How do I read a file into a JavaScript variable?
• How do I write a file from JavaScript?
• See also Cookies for information on cookie files.

Javascript Dates and Time

• How do I write a clock program in JavaScript?
• How do I determine the week day for a given date?
• Is JavaScript code vulnerable to the Year 2000 problem?
• See also Clock bookmarklet

Javascript Cookies

• How do I set a cookie from JavaScript?
• How do I read a cookie with a given name?
• How do I delete a cookie with a given name?
• How do I test whether cookies are enabled in the user's browser?
• Where are cookie files actually stored on the hard disk?

Javascript Client Information

• How do I detect the browser name (vendor)?
• How do I detect the browser version?
• How do I detect the operating system on the client machine?
• How do I get the screen size on the client machine?
• How do I get the browser window size?

Javascript Bookmarklets

• What's a bookmarklet?
• What browsers support bookmarklets?
• What's the maximum length of bookmarklet code?
• Bookmarklet example: Calculator
• Bookmarklet example: Clock
• Can I have a JavaScript interpreter bookmarklet?

Javascript Sound

• What browsers can execute scripts that play sound?
• Can I play a sound file without using JavaScript?
• How do I write a JavaScript function that plays a sound file?
• How do I write a JavaScript function that stops playing sound?
• Can I play a sound onMouseOver?
• How do I preload a sound file?
• How do I set a background sound on a Web page?
• Which formats of sound files can I play on my Web page?

Javascript Error Handling

• Can I suppress JavaScript error messages?
• Can I set up my own JavaScript error handler?
• Can I change the active JavaScript error handler? (Demo)

• Index

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The JavaScript FAQ
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