product.js

class Product {
  
  constructor(name) {
    this.name = name;
  }
  
  setName(name) {
    this.name = name;
    // Return this for chaining
    return this;
  }
  
  setPrice(price) {
    this.price = price;
    // Return this for chaining
    return this;
  }
  
  save() {
    console.log(this.name, this.price, this.units);
    // Return this for chaining
    return this;
  }
}

const product = new Product("T-Shirt")
    .setName("Jeans")
    .setAge(31.99)
    .save();