Can I use in Google Apps Scripts a defined Class in a library with ES6 (V8)?

Question

I'm trying to use a class defined in a library but I only receive an error as a result.

[LibraryProject]/library/model/Update.gs

class Update {
  constructor(obj = {}) {
    if(typeof obj == "string"){
      options = JSON.parse(obj);
    }
    Object.assign(this, obj);
  }

  text(){
    return (this.message && this.message.text)?this.message.text:''
  }
}

TASKS

✅ Create a new version of the project. (File > Manage versions...)

✅ Load this library in another project [Alias: CustomService] (Resources > Libraries...)

✅ Use functions of CustomService

❌ Use class of CustomService

If I try to use a Class

[NormalProject]/index.gs

function test  (){
  Logger.log(CustomService.libraryFunction())
  var update = new CustomService.Update("");
  Logger.log(update)
}

TypeError: CustomService.Update is not a constructor (línea 3, archivo "Code")

How can I instantiate an Object of this Class?

If I run...

Logger

score 9 · Accepted Answer · answered Feb 28 '20 at 21:55

As written in the official documentation,

Only the following properties in the script are available to library users:

enumerable global properties

function declarations,

variables created outside a function with var, and

properties explicitly set on the global object.

This would mean every property in the global this object are available to library users.

Before ES6, All declarations outside a function (and function declaration themselves) were properties of this global object. After ES6, There are two kinds of global records:

Object record- Same as ES5.

Function declarations

Function generators

Variable assignments

Declarative record - New

Everything else - let, const, class

Those in the declarative record are not accessible from the global "object", though they are globals themselves. Thus, the class declaration in the library is not accessible to library users. You could simply add a variable assignment to the class to add a property to the global object(outside any function):

var Update = class Update{/*your code here*/}

References:

the factory method solution is working, but I'll this approach to see if it works. Thanks — raultm, Feb 29 '20 at 08:17
this works but we still can't see the documentation for that class or its methods, any solution that allow the documentation to pass through? — Legion, Mar 23 '20 at 22:07
@Legion Documentation doesn't pass through. AFAIK, Only documentation that are supported are ``@param``and ``@returns``: Both of which are useless here. — TheMaster, Mar 24 '20 at 02:53

score 4 · Answer 2 · answered Feb 28 '20 at 17:52

Based on your tests, it appears that you cannot directly import a class from a GAS library. I'd recommend creating a factory method to instantiate the class instead.

Something along these lines:

// Library GAS project

/**
 * Foo class
 */
class Foo {
    constructor(params) {...}

    bar() {...}
}

/* globally accessible factory method */
function createFoo(fooParams) {
    return new Foo(fooParams);
}

// Client GAS project

function test() {
    var foo = FooService.createFoo(fooParams);
    Logger.log(foo.bar());
}

Ok. I needed to do some fixes but it works. Thanks for the easy solution. Factory methods! — raultm, Feb 28 '20 at 18:57

Can I use in Google Apps Scripts a defined Class in a library with ES6 (V8)?

2 Answers2

References:

Linked

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