How to declare a custom class in google scripts?

I want to create a class inside my script.

Google Apps Script language is based on javaScript, so I took an example from a javaScript manual:

class Polygon {
  constructor(height, width) {
    this.height = height;
    this.width = width;
  }
}

However, this doesn't work. I get this error message:

Missing ; before statement. (line 1, file "Code")

Does that mean it's not possible to create new classes in google scripts?

Or is there a different syntax I'm supposed to use?

Solved

Historically Javascript is a "classless" language, classes are a newer feature which haven't been widely adopted yet, and apparently are not yet supported by Apps Script.

Here's an example of how you can imitate class behaviour in Apps Script:

var Polygon = function(height, width){
  this.height = height;
  this.width = width;

  this.logDimension = function(){
    Logger.log(this.height);
    Logger.log(this.width);
  }
};

function testPoly(){
  var poly1 = new Polygon(1,2);
  var poly2 = new Polygon(3,4);

  Logger.log(poly1);
  Logger.log(poly2);
  poly2.logDimension();
}