Programmatically control breakpoints in Javascript?

Question

Is it possible, in any browser, using any plugin, to enable or disable breakpoints in your code programmatically?

I already know about setting conditional breakpoints, but I'm really interested in setting them via code.

Answer 1

First you could add a call to a function like __checkDebug(); which will check for a global (or semi-global) variable and when said variable is true, call debugger.

   function __checkDebug() {    if (debugme) debugger; }  

all of your functions you're concerned about debugging would be like so:

   function foo() {    __checkDebug();     //.... whatever foo was gonna do. }  

You can then take it a little further and dynamically decorate functions while the code is being executed like so:

 Function.prototype.debug = function(){       var fn = this;     return function(){             if (debugme) debugger;         return fn.apply(this, arguments);         };  };   foo = foo.debug();    

now any time foo is called it will call debugger if the debugme variable is truthy.

Another option would be to build a javascript build system that injects the call after every function declaration - this requires a syntax parser but if you're only looking to modify functions a simple tokenizer for that use case is pretty easy to write - but I'll leave that up to you.

Answer 2

You can use debugger; in code to make breakpoint for firebug. For example:

alert('1'); debugger; alert('2'); 

And firebug automatically stops on this keyword.