script.js

// Fluent api

function Chai() {}

Chai.prototype.expect = function(number) {
  this.number = number;
  return this;
};

Chai.prototype.increment = function() {
  this.number += 1;
  return this;
};

Chai.prototype.decrement = function() {
  this.number -= 1;
  return this;
};

Chai.prototype.addTo = function(num) {
  this.number -= num;
  return this;
};
var chai = new Chai(1);
chai.expect(5).increment();