give a class property a type js code example

Example 1: javascript classes

class SayHelloTo {
  name (to) {
    console.log(`Hello ${to}`);
  }
  constructor (to) {
    this.name(to);
  }
}
const helloWorld = new SayHelloTo(World);

Example 2: es6 class example

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