Mega Code Archive
Debug function displays plain-text debugging messages
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/*
Examples From
JavaScript: The Definitive Guide, Fourth Edition
Legal matters: these files were created by David Flanagan, and are
Copyright (c) 2001 by David Flanagan. You may use, study, modify, and
distribute them for any purpose. Please note that these examples are
provided "as-is" and come with no warranty of any kind.
David Flanagan
*/
/**
* This debug function displays plain-text debugging messages in a
* special box at the end of a document. It is a useful alternative
* to using alert() to display debugging messages.
**/
function debug(msg) {
// If we haven't already created a box within which to display
// our debugging messages, then do so now. Note that to avoid
// using another global variable, we store the box node as a property
// of this function.
if (!debug.box) {
// Create a new <div> element
debug.box = document.createElement("div");
// Specify what it looks like using CSS style attributes
debug.box.setAttribute("style",
"background-color: white; " +
"font-family: monospace; " +
"border: solid black 3px; " +
"padding: 10px;");
// And append our new <div> element to the end of the document
document.body.appendChild(debug.box);
// Now add a title to our <div>. Note that the innerHTML property is
// used to parse a fragment of HTML and insert it into the document.
// innerHTML is not part of the W3C DOM standard, but it is supported
// by Netscape 6 and Internet Explorer 4 and later. We can avoid
// the use of innerHTML by explicitly creating the <h1> element,
// setting its style attribute, adding a Text node to it, and
// inserting it into the document, but this is a nice shortcut
debug.box.innerHTML =
"<h1 style='text-align:center'>Debugging Output</h1>";
}
// When we get here, debug.box refers to a <div> element into which
// we can insert our debugging message.
// First, create a <p> node to hold the message
var p = document.createElement("p");
// Now create a text node containing the message, and add it to the <p>
p.appendChild(document.createTextNode(msg));
// And append the <p> node to the <div> that holds the debugging output
debug.box.appendChild(p);
}
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