Why this code results in NaN?

Question

var x = 4;

var y = 5;

var d = 4 + z;

var z = y - x;

var c = x+z+d+y; alert(c);

Answer 1

DO NOT PUT CODE IN THE TITLE SECTION. Put it in the description part or link it.

Answer 2

"z" has not been defined when using it in line 3, 4 + undefinded is not a number.

In strict mode, this code may not work.
edit: Seems to work in strict mode.

Answer 3

Keep in mind. Code in JavaScript is read and executed from top to bottom, following the order in which it appears in the script.

Answer 4

at the time "d" is declared, "z" is not defined yet, resulting in undefined, this makes any calculation on it worthless (still results in undefined)

Answer 5

Probably using Z before it's defined.

But var accepts hoisting so the result should result 15.

Answer 6

OK Lisa

Answer 7

Strict mode?

Answer 8

Umer
In 3rd statement you didn't even defined z variable and using it for sum. You have define it later.

And what you even mean by strict mode?

Answer 9

Try using
alert(int(c));