Triggers (onEdit, onOpen) in Google Sheets - Cell-by-Cell Formula Trace

Sample Data

A simple score table with names and scores.

Cell	Value
A1	Name
B1	Score
A2	Alice
B2	85
A3	Bob
B3	90
A4	Charlie
B4	78

Formula Trace

onEdit(e) and onOpen() are Google Sheets triggers that run scripts automatically when you edit a cell or open the spreadsheet.

Step 1: User edits cell B2 from 85 to 88

Step 2: Script reads the edited cell B2 value (88)

Step 3: Script updates cell C2 with 'Updated!'

Step 4: User opens the spreadsheet

Step 5: Script adds a custom menu 'My Menu' to the spreadsheet UI

Cell Reference Map

Name

↓

Alice

↓

Bob

↓

Charlie

Cells A1:B4 hold data. Cell B2 is edited triggering onEdit. Cell C2 is updated by script. onOpen affects the whole spreadsheet UI.

Result

   A       B       C
1 Name    Score   
2 Alice   88     Updated!
3 Bob     90     
4 Charlie 78     

Menu: 'My Menu' appears in toolbar

After editing B2 to 88, cell C2 shows 'Updated!'. When the sheet opens, a custom menu 'My Menu' appears in the toolbar.

Sheet Trace Quiz - 3 Questions

What event causes the onEdit trigger to run?

A When a user changes a cell value

B When the spreadsheet is opened

C When a formula recalculates

D When a new sheet is added

Key Result

Triggers like onEdit and onOpen run scripts automatically on user actions like editing cells or opening the sheet.

Practice

1. What does the onOpen trigger do in Google Sheets?

easy

A. Saves the spreadsheet automatically

B. Runs a script automatically when the spreadsheet is opened

C. Runs a script when a cell is edited

D. Deletes all data when the sheet is opened

Solution

1. Step 1: Understand the purpose of onOpen

   The onOpen trigger runs a script automatically when the spreadsheet is opened by a user.

2. Step 2: Compare with other triggers

   Unlike onEdit, which runs on cell changes, onOpen activates only on opening the file.

3. Final Answer:

   Runs a script automatically when the spreadsheet is opened -> Option B

4. Quick Check:

   onOpen = runs on open [OK]

Hint: Remember: onOpen triggers when file opens, not on edits [OK]

Common Mistakes:

• Confusing onOpen with onEdit trigger
• Thinking onOpen runs on every cell change
• Assuming onOpen saves the file automatically

2. Which of the following is the correct way to define an onEdit trigger function in Google Sheets Apps Script?

easy

A. function onEdit(e) { /* code here */ }

B. function onEdit { /* code here */ }

C. function onEdit() { /* code here */ }

D. function onEdit(e) => { /* code here */ }

Solution

1. Step 1: Recall correct function syntax with event object

   The onEdit trigger function must accept an event object parameter e to access edit details.

2. Step 2: Check syntax correctness

   function onEdit(e) { /* code here */ } uses correct function declaration with parameter e and braces.

3. Final Answer:

   function onEdit(e) { /* code here */ } -> Option A

4. Quick Check:

   onEdit needs (e) parameter and braces [OK]

Hint: Include (e) parameter to access edit info in onEdit [OK]

Common Mistakes:

• Omitting the (e) parameter in onEdit function
• Using arrow function syntax which is invalid here
• Missing parentheses or braces in function declaration

3. Given this onEdit function in Google Sheets Apps Script:

function onEdit(e) {
  if (e.range.getA1Notation() === 'A1') {
    e.source.getActiveSheet().getRange('B1').setValue('Edited!');
  }
}

What happens when you edit cell A1?

medium

A. Nothing happens

B. Cell A1 will be cleared

C. Cell B1 will display the text 'Edited!'

D. An error occurs because of wrong syntax

Solution

1. Step 1: Understand the trigger condition

   The function checks if the edited cell is 'A1' using e.range.getA1Notation().

2. Step 2: Analyze the action on condition true

   If true, it sets the value of cell 'B1' to 'Edited!' on the active sheet.

3. Final Answer:

   Cell B1 will display the text 'Edited!' -> Option C

4. Quick Check:

   Editing A1 triggers B1 = 'Edited!' [OK]

Hint: Check edited cell with e.range.getA1Notation() [OK]

Common Mistakes:

• Assuming the edited cell changes instead of B1
• Thinking the script clears A1
• Believing the code has syntax errors

4. This onOpen function is intended to show a custom menu, but it doesn't work:

function onOpen() {
  var ui = SpreadsheetApp.getUi;
  ui.createMenu('My Menu')
    .addItem('Say Hello', 'sayHello')
    .addToUi();
}

What is the error?

medium

A. Missing parentheses after getUi

B. Function onOpen must have parameter e

C. createMenu is not a valid method

D. addItem requires two parameters

Solution

1. Step 1: Identify method call syntax

   The code uses SpreadsheetApp.getUi without parentheses, so it references the function but does not call it.

2. Step 2: Correct method call

   Adding parentheses getUi() calls the method and returns the UI object needed to create the menu.

3. Final Answer:

   Missing parentheses after getUi -> Option A

4. Quick Check:

   Method calls need () to execute [OK]

Hint: Always add () to call methods like getUi() [OK]

Common Mistakes:

• Forgetting parentheses on method calls
• Thinking onOpen needs parameters
• Misunderstanding addItem parameters

5. You want to create an onEdit trigger that automatically timestamps column B when a user edits column A in the same row. Which script correctly does this?

hard

A. function onEdit(e) {
if (e.range.getColumn() === 2) {
var row = e.range.getRow();
e.source.getActiveSheet().getRange(row, 1).setValue(new Date());
}
}

B. function onEdit(e) {
if (e.range.getColumn() === 1) {
e.source.getActiveSheet().getRange('B' + e.range.getRow()).setValue('Timestamp');
}
}

C. function onEdit(e) {
if (e.range.getRow() === 1) {
e.source.getActiveSheet().getRange('B1').setValue(new Date());
}
}

D. function onEdit(e) {
if (e.range.getColumn() === 1) {
var row = e.range.getRow();
e.source.getActiveSheet().getRange(row, 2).setValue(new Date());
}
}

Solution

1. Step 1: Check column condition for edits in column A

   The script must detect edits in column 1 (A) using e.range.getColumn() === 1.

2. Step 2: Set timestamp in column B of the same row

   It gets the row number and sets the current date/time in column 2 (B) of that row using setValue(new Date()).

3. Final Answer:

   function onEdit(e) { if (e.range.getColumn() === 1) { var row = e.range.getRow(); e.source.getActiveSheet().getRange(row, 2).setValue(new Date()); } } -> Option D

4. Quick Check:

   Detect col A edit, timestamp col B same row [OK]

Hint: Use getColumn() and getRow() to target cells dynamically [OK]

Common Mistakes:

• Checking wrong column number for edits
• Using fixed cell references instead of dynamic rows
• Setting text instead of actual timestamp