Please help

Question

var a = 1;
for (;a < 5; a++){
a+=a;
}

alert (a);

please explain this code.

Answer 1

first: a = 1 < 5 = true // a = 1+1 = 2 then + increment 1 = 3
sec: a = 3 < 5 = true // a = 3+3=6 then + increment 1 = 7
third: a = 7 < 5 = false // code stops

alert(a) // a = 7

Answer 2

Ben is right. sorry my bad

Answer 3

loop a=1 to 4
do a= old a + new a
effectively, a = 1+2+3+4
alert a i.e. a=10