JSDB

Overview

JSDB is a command line debugger modeled after jdb.

Supported Commands

Normal State:

load <filename>	Load and run a javascript file.
suspend	Stop before first instruction is executed
stop at <filename> <line>	Set a breakpoint. File doesn't have to be loaded yet.
clear at <filename> <line>	Clear a breakpoint.
bp	List breakpoints.
list <filename> <line>	Print source code.
scripts	List loaded scripts.
quit, exit	Quit jsdb.

Stopped State:

resume, exit	Resume execution.
stop at <filename> <line>	Set a breakpoint.
clear at <filename> <line>	Clear a breakpoint.
bp	List breakpoints.
list [<filename> <line>]	Print source code. If filename is not specified, prints the current line in the current stackframe.
up	Move up the stack.
down	Move down the stack.
where	Dump stack.
step	Execute current line.
eval <expr>	Evaluate expression in current frame. print() function is supported, so, for example, eval print(a) will print the value of variable a.

Example

sample.js:
______________________________________________________
a=1;
for (i=0; i<10; i++){
a = inc (inc(a));
}

c = a+2;

// Increment function
function inc (b){
return b+1;
}
______________________________________________________

A sample JSDB session could be:

>stop at sample.js:6
Script not loaded. Breakpoint will be set once the script is loaded
>load sample.js
Set breakpoint at sample.js null 6
Stopped at 6
STOPPED >>list
c = a+2;
STOPPED >>eval print (a)
21
STOPPED >>resume
>

Notes

I didn't test JSDB much, so I'm sure that there are some bugs. If you find one, or if you have a suggestion, please e-mail me.

Bugs and "features"

Important: JSDB crashes when executed with jits. Use -nojit switch if you are using jre.exe.

Alex Rakhlin
rakhlin@netscape.com