How to perform method chaining in JS

method_chaining_in_js.js

// Source: https://www.typescriptlang.org/play?target=1&ssl=42&ssc=3&pln=21&pc=1&q=316#code/PTAEDEFcDsGMBcCWB7apYAsCGjq4OagCCACgJIDOoWATgKbXrIC2zqoADlvPHTWrgBQIUACksANywBlWDUQd4AGlAB3DIkzosaZlgDWDAJ7JINJgBMGAM2SxIFOheFhVieBlAAbOhSq5eGmYnRFojUCkvSF9qaAtQOiwKRD5QeGRQeixnEQAjOlgsBwZkazSMOkRzaF8kaEIAR0gsL3cUigA6QRdiTMSvL3DYFjY0UjI1DS1VZBp9KglQ9GxcAh7EKgArAEVomiMO0AAJPgYN2ISADyxmDh9QUtAdvaMe-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-1+Hy4NJFQRB+qdIlUOVnDyFIvC6eF0CRXwxmVTmNBtukNBSVhhlWdasW2R4GwdHpmEyTluWFZwkC5K0sA8SFcDRWVzXU50dP87ToAJShsCdX0rHrmWjPMxwrPsyjJW83FpnVXQtXIPVQuNRL-XlBsstMx99A-pi5y4NQhaoHyNQ7XDFgI+dzp3a9Zqu8FD3yE9Htve6IilucZ5MvcXx-CWiI9go8A9ACQIodYpxwP8GTNjGiBWIwC71sgPRp4smfpNVHyjl2MhyNHnDcGhnSjRAsxjrMDDB45VChmWKIgD0oAALSA8ySLDFYPfWDNQA

// Here is an example API which creates a chaining
// API. The key is to have an outer function which
// keeps track of internal state, and an object which
// exposes the API that is always returned.

const addTwoNumbers = (start = 1) => {
  let n = start;

  const api = {
    // Implement each function in your API
    add(inc: number = 1) {
      n += inc;
      return api;
    },

    print() {
      console.log(n);
      return api;
    },
  };
  return api;
};

// Which allows the same style of API as we
// saw in jQuery:

addTwoNumbers(1).add(3).add().print().add(1);


// Here's a similar example which uses a class:

class AddNumbers {
  private n: number;

  constructor(start = 0) {
    this.n = start;
  }

  public add(inc = 1) {
    this.n = this.n + inc;
    return this;
  }

  public print() {
    console.log(this.n);
    return this;
  }
}

// Here it is in action:

new AddNumbers(2).add(3).add().print().add(1);