Javascript Debugging Assignment Help

Javascript Debugging

Errors are also called as bugs. The task of finding and rectifying the errors are called as debugging in program scenario.

28.1 Internet Explorer and Javascript errors

When an error encountered in Javascripting program, that will be indicated in the status bar of the Internet Explorer Browser with the error icon

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The error descriptions will be occurred when double clicking on the error icon.

Internet Explorer can display Error dialog box by default whenever an error occurs. To display error dialog box automatically we have check the following option. select Tools → Internet Options → Advanced tab. and then finally check the "Display a Notification About Every Script Error" box option.

28.2 Firefox or Mozilla and Errors

In Firefox, Netscape, and Mozilla browsers bug messages are viewed in a distinctive window called the JavaScript Console or Error Console. To enable the console, select Tools → Error Console or Web Development.

28.3 How to debug a Script

There are various methods to debug your JavaScript program:

28.4 JavaScript Validator

Validator is a tool which is used to verify each line of scripting program for parsing. It display the parsing errors.

Many free Javascript validators are available in the market. Examples include Douglas Crockford's JavaScript Lint etc.,

28.5 Add Debugging Code to Your Programs

The programmers can add their own debugging code with the help of the methods alert( ) and document.write( ).

Example

{`
var debug=true;
if(debug)
	alert(“This block of code goes wrong”);
  `}

28.6 Use a JavaScript Debugger

Using the Javascript debugger application the programmer can visualize the flow of execution of the program. Using this application the programmers can easily catch the bugging place which affects the smooth execution of program.