I expected fnc prints MyClass, at least the last one, but actually it printed undefined.

this.js

'use strict'

function MyClass() { 
  function fnc() { 
    console.log(this, 'in fnc');
  } 
  const arrow = () => { 
    console.log(this, 'in arrow');
  } 
  const bind = function() { 
    console.log(this, 'in bind');
  }.bind(this)
  this.method = () => { 
    fnc(); // undefined
    arrow(); // MyClass
    bind(); // MyClass
    console.log(this, ' in method.'); // MyClass
  } 
  fnc(); // undefined
}

const obj = new MyClass();
obj.method();