# ES6 Currying

Observe the code below:
```
const sum = a => b => a + b;
```
Let's try to understand the above code.

In the above code snippet, there are two function, `sum` and the anonymous function returned by `sum`. The `sum` takes one argument and the anonymous function returned by `sum` requires one argument.

To understand the above function better lets call it.

```
const sum = a => b => a + b;
console.log(sum(2)(3));
```

The console output of the above snippet will be `5`. The `sum` function took `2` as an argument and returned an anonymous function. The function returned by `sum(2)` can be written as:

```
/* pseudocode just for the sake of understanding */
sum(2) returns b => 2 + b;
```

Next, the anon is passed with argument `3`, and it returns sum of `2+b` that is `2+3`.  And finally the result is shown on the console.

So, the above curried arrow function code can also be written as:

```
const sum = function(a) {
    return function(b) {
        return a + b;
    }
}

console.log(sum(2)(3));
```

---
*Reference:*
[Codekirei](http://codekirei.com/posts/currying-with-arrow-functions/)