Why is this code outputting 21

Question

https://code.sololearn.com/W28HoBFte4i4/?ref=app

Answer 1

E∆SI 🇳🇬 Before your alert on line 4, you have an array of length 3 like this:

var a = new Array();
a = [, 2, 1]

So, alert([2] + a.length - a[1]) will convert the first part which is an array with 2 to a string "2" because of the + operator. Your array.length is 3 because you inserted two items in index positions 1 and 2, so a placeholder item exists in index position 0.

Now we have "2" + 3 which becomes the string "23".

You then subtract from that the item at index position 1 of your array which is 2.

The final calculation is "23" - 2 which comes to "21".

Answer 2

CamelBeatsSnake
🅰🅹 (Challenge Accepted)

Thanks so much

Answer 3

E∆SI.py 🇳🇬

Because [2] + 3 - 2 = [2] + 1 = 21

Answer 4

E∆SI 🇳🇬 You're welcome.