I want to Split a number into its digit (for example 4563 to 4 , 5 , 6 , 3 ) then addiction this digits. (for example: 4+5+6+3=18)

I can write code for 3 digit or 2 digit and ... numbers seperately but I cant write a global code for each number.

so this is my code for 2 digit numbers:

```
var a = 23
var b = Math.floor(a/10); // 2
var c = a-b*10; // 3
var total = b+c; // 2+3
console.log(total); // 5

```

and this is my code for 3 digit numbers:

```
var a = 456
var b = Math.floor(a/100); // 4
var c = a-b*100; // 56
var d = Math.floor(c/10); // 5
var e = c-d*10; // 6
var total = b+d+e; // 4+5+6
console.log(total); // 15

```

but I cant write a code to work with each number.How can I write a global code for each number?