The basic terminology of coding applies to Apps Script (check out the Introduction to coding page if you've not already and you're new to coding), so you'll find things like variables, comments, conditions, and loops are all features. The first thing you tend to learn how to do is to create a variable, which is a value you've saved with a name so you can access it again in your code.

In Apps Script, a variable can contain not only individual values and lists of values (called arrays), but also whole spreadsheets or documents.

To create a variable, you must tell Apps Script it is a new variable using the keyword var and then give it a name. You then assign it a value using the equals sign =, which in coding is the assignment operator, and enter the value of the variable after the equals sign. So you might have something like:

var startingValue = 0;

As the name 'variable' suggests, the value of a variable can be changed, so

startingValue = 1;

would change the value of startingValue to 1.

You can also write a line of code that has an output and have that after the equals sign when creating a variable, so you could for example create a variable that is assigned the value of the outcome of a calculation, or which uses one of the Apps Script apps to store a spreadsheet in it, like:

var ss = SpreadsheetApp.getActiveSpreadsheet();

When you're first learning Apps Script, it can be helpful to try out creating different kinds of variables and using the Logger to check their value by viewing the Execution Log, so you know you're doing it correctly:

Logger.log(startingValue);

Data types in coding tell the computer what kind of data is stored in the variable, which then allows different kinds of things to be done with that data. For example, if you add together two numbers, you'll get a numerical answer, but if you add together two text strings, you will concatenate them (join them together).

Some of the key data types you'll use in Apps Script are: numbers; strings (a collection of characters that can include text, numbers, punctuation and spaces); and arrays (a list of values stored together, which can contain other data types including arrays themselves).

To create these data types, you use particular syntax. For example, numbers are entered without punctuation, but strings need to be surrounded by single or double quotes, and arrays must be surrounded by square brackets and each item in an array must be separated by a comma.

var number = 7;
var text = "Apps Script";
var things = [7, "Apps Script", 998.87];

In Apps Script (and JavaScript) you can change the data type of a value just by assigning it a new value.

Arrays

As we've already mentioned, arrays contain multiple items in one variable, and can contain different data types including other arrays. In Apps Script, if you get the values from a spreadsheet, for example, these will be in the array data type, so it is useful to know how to use and navigate arrays. We'll take a look at how to access specific values from within an array.

If you have a single array, for example:

var session = ["Intro to Google", "Online", 50];

you can access the individual values using index numbers within square brackets

session[1];

would give the output of Online.

This may seem counterintuitive, because "Online" is the second item in the array, but index numbers in arrays in coding start from 0, so the first item is index number 0, the second item is index number 1, and so on. This can catch you out, so it's always worth using the Logger.log() command to check what variable you have when you're first trying to access a particular value in an array.

If you have one or more arrays stored within an array, like

var courseList = [["Intro to Google", "Online", 50], ["More Drive tips", "Face to face", 15], ["Using Google Docs more", "Online", 75]];

then you have to use two index numbers to access individual values, and a single index number to access one of the sub-arrays. We often call this kind of array a two-dimensional (2D) array and it is often used in Apps Script to represent individual rows in a spreadsheet as the sub-arrays and then the main array is the whole spreadsheet. For example, getting one sub-array (which might be one line of a spreadsheet):

courseList[2];

would ouput ["Using Google Docs more", "Online", 75] and

courseList[2][0];

would output Using Google Docs more.

If you want to get your head round arrays a bit more, you can take a look at our Exercises with arrays.

When creating a new Apps Script project, you have to decide if it will be bound to another Google Drive file (like a spreadsheet) and accessible via the Apps Script editor or unbound, which means that the Apps Script project file itself will sit on Google Drive. In most cases, Apps Script projects bound to a particular file are most useful, as typically there will be a spreadsheet of data or form responses you want the script to work with and it makes sense to keep these connected.

To create a bound Apps Script project, you create or open a Google Sheets file, then go to Extensions > Apps Script and the Apps Script editor will open. You can then name your project, and rename the default "Code.gs" file to something more specific. Typically you'll also rename the default function myFunction with a more descriptive name for your code too.