Debugging in Apps Script

July 11, 2025

🛠 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

Open the script editor
Click on the bug icon 🐞 next to the function you want to debug
Optionally, add breakpoints (ctrl + b)
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.

Code Block Only

JSCode.gs


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

  onEdit(mockEvent);
}

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.