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NodeJS ECMAScript 2015 ES6

const/let declarations

Unlike var, const/let are bound to lexical scope rather than function scope.

 var x = 1 // will escape the scope
 let y = 2 // bound to lexical scope
 const z = 3 // bound to lexical scope, constant
console.log(x) // 1
console.log(y) // ReferenceError: y is not defined
console.log(z) // ReferenceError: z is not defined

Arrow functions

Arrow functions automatically bind to the 'this' lexical scope of the surrounding code.

performSomething(result => {
 this.someVariable = result


performSomething(function(result) {
 this.someVariable = result


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