How to declare Class fields

Question

I'm trying to create a class with some fields on Google Apps Scripts. I can't even save the file. From what I understand of this SO answer, I'm using the correct syntax for class fields.

V8 runtime is enabled.

The error:

Syntax error: ParseError: Unexpected token = line: 5 file: Airtable_Class.gs

Line 5 is: foo = "bar";

Here's the whole code:

class FieldsTest{
  foo = "bar";
}

https://stackoverflow.com/questions/68044338/declaring-private-variables-in-a-class-google-apps-script-v8 — Yuri Khristich, Feb 08 '22 at 23:09
The article that answer references includes, I think, the syntax I'm using: https://v8.dev/features/class-fields#public-class-fields — DBWeinstein, Feb 08 '22 at 23:14
Well. Many of examples from the article don't work. I have no idea what's going on. — Yuri Khristich, Feb 08 '22 at 23:19

score 6 · Accepted Answer · answered Feb 09 '22 at 07:13

6

This is a known issue. Add a star (★ on top left) to the issue, if you want this to be implemented.

https://issuetracker.google.com/issues/195752915

According to the tracker, it is supported, but it is blocked by the parser.

answered Feb 09 '22 at 07:13

TheMaster

45,448
6
62
85

SonGuhun · Answer 2 · 2023-02-21T18:27:35.013

There's a way to simulate static fields in Apps Script. It involves using properties instead of a field. We can create a lazily initiated property that replaces itself with a field, using the following code:

class MyClass {

  static get c() {
    // Delete this property. We have to delete it first otherwise we cannot set it (due to it being a get-only property)
    delete MyClass.c;
    // Replace it with a static value.
    return MyClass.c = {};
  }

}

This approach is better than using a static property, because it also works when instantiating static objects or arrays. To confirm this works, we can use the following:

SpreadsheetApp.getUi().alert(MyClass.c === MyClass.c)

This will only evaluate to true if the object was generated once and stored. If the field remains a property, it will return false, because the object is generated twice.

score 0 · Answer 3 · answered May 18 '22 at 14:10

Although it seems that Google Apps Script doesn't support static class fields, it does support static methods/getters/setters, so you can do this:

class X {
   // ⭐️ static getters & setters
   static get a(){ return this._a || 0 }     // this === X
   static set a(value){ this._a = value }    // this === X
}

then you can get/set X.a as usual:

X.a      // get: 0.0
X.a = 3  // set: 3.0
X.a      // get: 3.0

How to declare Class fields

3 Answers3

Linked

Related