Script Debugger can run a script. In fact, it can run (and debug) multiple scripts simultaneously. To execute (run) a script:

• Choose Script > Execute (or click the Execute button in the toolbar).

If the script needs compiling, Script Debugger attempts compilation first. If there is a compilation error, the script won’t start to run.

Otherwise, the script runs. While a script is running:

• A circular progress indicator spins at the right end of the title bar.
• Whenever an Apple event has been sent to an application but the application has not yet replied, the application’s icon appears at the right end of the title bar.

• In the toolbar, all buttons go dim except for the Stop button. You can click this, or choose Script > Stop, to interrupt execution.
• In the Script menu, the Execute menu item changes to Running and has a check mark.
• In the Window menu (and the Windows Inspector), the listing for this script window is badged with an icon indicating that it is running.

Additionally, if the script is in debug mode, then when the script is executing, the Pause button is enabled (along with Script > Pause).

When execution ends, the circular progress indicator goes away, and the Stop button is disabled. If no uncaught runtime error was encountered — that is, if the script ran all the way to a natural conclusion — there is usually a result.

When you start to execute a script, Script Debugger automatically saves a copy of the script in a private location. If execution of the script happens to crash Script Debugger (which can occur if a target application is particularly badly behaved), just start up Script Debugger again. Your script will be opened automatically, magically restored, just as it was when you started to execute it.

Note that you can control the execution of the frontmost script even when you’re in a different application! Use Script Debugger’s Dock menu. It contains Execute and Stop menu items (and others).

Script Debugger helps you run individual handlers in a script.