Provide quick understanding of ES6 Arrow functions.

arrow-functions.js

/*
  Arrow functions are a shorthand for anonymous functions in JavaScript.
  Unlike function, arrows share the same lexical `this` as their surroundings bodies.
*/

//Expression bodies
var result = items.map(v => v + 1);
var result = items.map((v, i) => v + i);
var result = items.map((v, i) => ({item: v, key: i}));

//Statement body
items.forEach(item => {
  if(item % 2 === 0){
     result.push(item);
  }
});

//Lexical body
var student = {
  name: 'Hashir',
  subjects: [],
  printSubjects() {
    this.subjects.forEach(sub => {
       console.log(`${this.name} knows ${sub}`);
    });
  }
};

student.subjects = ['Math', 'Science', 'English'];
console.log(student.printSubjects()); 
/*print:
Hashir knows Math
Hashir knows Science
Hashir knows English
*/