JS Challenges questions

Question

Hi, while doing JS challenges I came across these two questions which solution I still cant figure out.
1. Question
var nums1 = [1,2];
var nums2 = [3,4];
var set = nums1 + nums2;
console.log(set.length); // Output: 6
2. Question
var x = 1, y = 1, z = 0;
do{
z = x + y;
}
while(++x <= 1 && y++ >= 1);
z += x + y;
document.write(z); // Output: 5
Can someone please help me and explain it? Thanks a lot in advance.

Answer 1

Arrays have their own implementation of toString method that returns a comma separated list of elements:
let arr = [1, 2, 3, 4];
console.log(String(arr) === '1,2,3,4'); //true

Answer 2

1.adding two arrays using '+' will return string
2.understand how do while loops work
understand how that && works
first iteration x = 1,y = 1
so,z = 2
then > ++x <= 1
x will increment to 2 first then compare
the statement become false, and what comes after the statement (y++>=1) wont get executed
now z = 2,x = 2,y = 1
z = 5
just understand the basic how things work..then u can solve the question✌

Answer 3

https://www.sololearn.com/post/161927/?ref=app

Answer 4

1. Type conversation to string.
You have: 1,23,4.length => 6

Answer 5

Thanks alot everyone!