javascript

Chapter 14: Error Handling and Debugging
Stepping through Code
You can step through code on the Source tab using the buttons in the upper - left corner. There are six
buttons to control the execution of code and one for logging threads (see Figure 14 - 32 ).
Continue
Step Into
Step Over
Log Threads
Break on Error
Break Next
Step Out
Figure 14-32
The first four buttons are standard: Continue, Step Into, Step Over, and Step Out. The next two buttons
indicate different times when the debugger can break. The first of these is Break Next, which breaks into
the debugger when the next line of JavaScript is to be executed; the second is Break on Error, which
breaks into the debugger whenever an error occurs.
When code execution is stopped, the Call Stack and Inspection tabs are filled with information about the
current execution context.
The Command Line Tab
The last tab under the Scripts tab is called Command Line, and it contains a command - line console
similar to Firebug (see Figure 14 - 33 ).
Figure 14-33
Using the Command Line, you can execute JavaScript in the context of the currently loaded page and get
the result. Note that Opera doesn ’ t expose the console object, so you cannot write to this console from
JavaScript.
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