2.3.1 debugger Statement
The debugger statement causes a breakpoint to be entered if a debugger is available. If a debugger does not exist or is not active, this statement has no observable effect.
In JScript 5.x implementations, the debugger statement is evaluated as follows:
If a debugger is not available or is not active for this statement, return (normal, empty, empty).
Otherwise, suspend execution and enter the debugger.
When the debugging action is complete, if the debugger supplies a completion result, return that result; otherwise, return (normal, empty, empty).