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Debug JavaScript with firebug

Logging on JavaScript using Firebug

You can use Firebug generate logs. This is a great way to finding errors in a page.

Execute the following code in Firefox.

 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
  <html>
  <head>
  <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
  <title>Untitled Document</title>
  </head>
  <body>
  <script type="text/javascript">
               var a = "w3";
               var b = " ";
               document.write(a,b);
               //console.log("%s%d", "w3", resource);
  </script>
  </body>
  </html>

The above code is intended to output "w3resource". But it shows "w3" only. So let's uncomment the line console.log("%s%d", "w3", resource); and run Firebug.

logging-javascript-firebug

So, now we can easily understand that resource is not defined. Check the code back, and yes, var b = "";



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