How to define global variable in Google Apps Script

Question

I see most examples from Google is they use only functions in a single giant script.

e.g. https://developers.google.com/apps-script/quickstart/macros

But in our style, we usually write all functions under a single namespace, such as

MyCompany = (MyCompany || {}); MyCompany.init = function () {     Logger.log('init');   };  function onOpen() {     var spreadsheet = SpreadsheetApp.getActiveSpreadsheet();     var menus = [{         name: "Init",         functionName: MyCompany.init     }];     spreadsheet.addMenu("Test", menus); }; 

However, when I run the code above, it return

"MyCompany is not defined." 

How to solve?

Answer 1

You might be better off using the Properties Service as you can use these as a kind of persistent global variable.

click 'file > project properties > project properties' to set a key value, or you can use

PropertiesService.getScriptProperties().setProperty('mykey', 'myvalue'); 

The data can be retrieved with

var myvalue = PropertiesService.getScriptProperties().getProperty('mykey'); 

Answer 2

In GAS global variables are not what they are in other languages. They are not constants nor variables available in all routines.

I thought I could use global variables for consistency amongst functions and efficiency as well. But I was wrong as pointed out by some people here at SO.

Global variable will be evaluated at each execution of a script, so not just once every time you run your application.
Global variables CAN be changed in a script (so they are not constants that cannot be changed by accident), but will be reinitialized when another script will be invoked.
There is also a speed penalty on using global variables. If within a function you use the same global variable two or more times, it will be faster to assign a local variable and use that instead.

If you want to preserve variables between all functions in your application, it might be using a cacheService will be best. I found out that looping through all files and folders on a drive takes a LOT of time. But you can store info about files and folders within cache (or even properties) and speed up at least 100 times.

The only way I use global variables now is for some prefixes and for naming widgets.