# HOF (Higher Order Function)

 It’s *higher-order* because instead of `strings, numbers, or booleans`, it goes *higher* to operate on `functions.`

#### Returning Function:

```javascript
Ex 1:

const add = function(x) {
    return function(y) {
       return x+y;
    }
}

const sum = add(2)(3); // 5
```

`add` requires two parameters, but not all at once. It’s a function asking for just `x`, that returns a function asking for just `y`. Again, this is only possible because JavaScript allows functions to be a return value — just like strings, numbers, booleans, etc. You can still supply `x` and `y` immediately, if you wish, with a double invocation

#### Function as Argument:

```javascript
Ex 2:

function MultiplyByTwo(a) {
    return 2 * a;
}

const multiply = function(num, fn) { // accepts number and function as argumnet
    return fn(num);
}

const result = multiply(3, MultiplyByTwo); // 6
```

`MultiplyByTwo` function multiplies the give number with 2. `multiply` function takes two argument first one as number and second is function. I have passed the number 3 and `MultiplyByTwo` function as an argument to `multiply` function.  `multiply` function will returns the `2 multiplied by 3 value as 6`