notes-node/playground/arrow-function.js

var square = x => x * x;

var user = {
  name: 'Pedro',
  // Arrow functions do not bind the 'this' keyword
  sayHi: () => {
    console.log(`Hi! I am ${this.name}`);
  },

  // Traditional functions do bind the 'this' keyword
  sayHiAlt: function() {
    console.log(`Hi! I am ${this.name}`);
  },

  /* This could also be written like this:
  sayHiAlt() {
    console.log(`Hi! I am ${this.name}`);
  }
  */

  // Arrow functions also don't bind the arguments array
  printArgs: () => {
    // This is not a local arguments array, but global arguments array
    // be careful!!
    console.log(arguments);
  },

  printArgsAlt() {
    // This is a local arguments array from function call
    console.log(arguments);
  }
};
user.sayHi();
user.sayHiAlt();

// Global args get printed
user.printArgs(3, 'sad tigers', 3, ' wheat dishes'); 

// { '0': 3, '1': 'sad tigers', '2': 3 ... } local arguments array as object
user.printArgsAlt(3, 'sad tigers', 3, ' wheat dishes'); 
console.log(square(9));