A `this` context reminder for NodeJS

this.js

#!/usr/bin/node

// non-strict mode = `this` context is 'global'
// strict-mode    = `this` context is undefined


function parentFunction() {
  this.foo = 'bar';

  console.log('parentFunction scope : ' + this.foo);
  console.log('parentFunction scope : ' + this);

  function firstLevelFunction() {
    console.log('firstLevelFunction scope : ' + this.foo);
    console.log('firstLevelFunction scope : ' + this);
  }

  const firstLevelArrowFunction = () => {
    console.log('firstLevelArrowFunction scope : ' + this.foo);
    console.log('firstLevelArrowFunction scope : ' + this);
  };

  firstLevelFunction();
  firstLevelArrowFunction();
}

parentFunction();

// set the context with call() method
parentFunction.call('superContext');