Exemplifying ES2015 sytanx

arrow-functions.js

// Basic syntax examples
var add = ( a, b ) => a + b; // function( a, b ) { return a + b; }
var increment = a => a + 1; // function( a ) { return a + 1; }
var random = ( ) => Math.random( ) // function( ) { return Math.random( ); } 

// Functional programming unleashed
var array = [ 'alice', 'bob', 'charles', 'dan', 'eugene', 'felicity' ];
var longNames = array.filter( name => name.length > 3 );
var longNamesIndexes = longNames.map( ( name, index ) => index );
var sumOfIndexes = longNamesIndexes.reduce( add );

// One liner mindfuck
var sumOfIndexes = array.filter( n => n.length > 3 )
                        .map( ( n, i ) => i )
                        .reduce( ( a, b ) => a + b );