Debugging in Apps Script

What is the Debugger?

The Apps Script debugger lets you pause your code at any point and step through it line-by-line to see what’s really happening. You can inspect variables, monitor execution flow, and identify exactly where your script is misbehaving.

How to Use the Debugger

1. Open the script editor
2. Click on the bug icon 🐞 next to the function you want to debug
3. Optionally, add breakpoints (ctrl + b)
4. Press the Debug button

You can explore every variable, global or scoped, and inspect your data in real time. 

Personally, I rely on the debugger while coding, especially when working on complex mapping algorithms. It’s a game-changer for understanding what’s happening under the hood.

Pro tip! If the function you want to debug relies on a trigger (like onEdit or onFormSubmit), you can build mock data to simulate the event and test your code manually.

function testOnEdit() {
  const mockEvent = {
    range: SpreadsheetApp.getActiveSheet().getRange("B2"),
    value: "test value",
    source: SpreadsheetApp.getActiveSpreadsheet()
  };

  onEdit(mockEvent);
}