Creating Custom Functions with Google Apps Script

While Google Sheets offers a vast library of built-in functions, there will be times when you need to perform a calculation or process data in a way that a standard function simply can't handle. This is where custom functions, created with Google Apps Script, become incredibly powerful. They allow you to extend the functionality of Google Sheets and tailor it to your specific needs, automating complex or repetitive tasks directly within your spreadsheets.

Think of custom functions as adding your own unique formulas to Google Sheets. You can write them in JavaScript using the Google Apps Script editor, and then use them in your spreadsheet just like any other function (e.g., SUM, AVERAGE). This section will guide you through the process of creating and using your first custom functions.

To get started, you'll need to access the Google Apps Script editor. Here's how:

1. Open your Google Sheet.
2. Go to the 'Extensions' menu.
3. Select 'Apps Script'.

This will open a new browser tab with the script editor. You'll see a default script file named 'Code.gs'. This is where you'll write your custom functions.

Let's create a simple custom function that calculates the area of a rectangle. In the Code.gs file, delete any existing code and paste the following:

javascript function CALCULATE_RECTANGLE_AREA(length, width) { return length * width; }

In this code:

• function CALCULATE_RECTANGLE_AREA(length, width): This line defines a new function named CALCULATE_RECTANGLE_AREA. The names of custom functions used in Sheets are typically written in all caps to distinguish them from built-in JavaScript functions.
• (length, width): These are the arguments or inputs your function will accept. When you use this function in Sheets, you'll provide values for length and width.
• return length * width;: This is the core logic of your function. It multiplies the length and width arguments and returns the result.

After writing your function, you need to save the script. Click the floppy disk icon (Save project) in the script editor, and give your project a name if prompted (e.g., 'My Custom Functions').