What is the output of this code?

Question

var a = 12;
var k = 7;
var y = a + 23;
var d = k + b;
d = 20;
document . write (d);
document . write(y);

Answer 1

It's quite easy:
Just resolve first the operations like:
K + b (==7+12) &
a + 23 (==12 +23)

Then it's a document.write, that output the result of the above operations.

Hope it helps :)

Answer 2

ReferenceError: b is not defined.