Arrow functions in ES-6

Code for this and several other ES-6 features can be found in my github

ES-6 introduced a shorthand notation to declare functions. In addition to this being a shorthand and being concise, there are a few other advantages specific to scoping that we will see in the next section.

Let us for example, consider a simple map reduce in Javascript ES-5:

var arr = [1,2,3,4,5];
var result = arr.map(
    function(a) {
        return a+1
    }).reduce(
        function(a,b){    
            return a+b
});

While the same thing can be written in ES-6 in a concise manner as follows:

var arr = [1,2,3,4,5];
var result = arr.map((a)=>a+1).reduce((a,b)=>a+b);
console.log(result);

About the syntax:

ES-6 arrow functions can be declared as constants as follows:

const add = (a,b)=> a+b;

and this function can be passed around or used in a way any other function in JS would be.

It is important to note that, if the function body is a single line there is no need for curly braces around the body. Which is why there are not curly braces around 

a+b;

And by default the result of a+b will be returned implicitly.

However, if the function body has multiple lines of code, for example:

const kindOfAdd = (a,b)=> {
let x = a+1;
let y = b+1;
return x+y;
}

If you see in the function

 kindOfAdd 

, the body has multiple lines. Hence it should be surrounded by curly braces and also the expected return value should be explicitly returned.