Ways to split a Number into an Array

Question

Let's say we have a number:

let num = 969

I'm trying to split this number into an array of digits. The first two methods do not work, but the third does. What is the difference?

num + ''.split('')             // '969'
num.toString() + ''.split('')  // '969'
String(num).split('')          // [ '9', '6', '9' ]

Answer 1

Well, let's look how it works

num + ''.split('') works like

1. num is a number
2. ''.split('') is empty array and it's not a number
3. so, we have sum of a number and not a number, we will cast num and [] to string
4. num to string is '969', [] to string is '' (empty)
5. '969' + '' = '969'

num.toString() + ''.split('') works like

1. num.toString() is a string
2. ''.split('') is empty array
3. so, we have sum of a string and not a string, we will cast [] to string
4. [] to string is '' (empty)
5. '969' + '' = '969'

String(num).split('') works like

1. lets cast num to string
2. and split it by ''
3. result of split is array ['9', '6', '9']

Answer 2

Try like this, you will understand why !

(num + '').split('')             // [ '9', '6', '9' ]
(num.toString() + '').split('')  // [ '9', '6', '9' ]
String(num).split('')          // [ '9', '6', '9' ]

in the first and second lines, you split '' (empty string).