Could anyone explain the answer to this question from the “play” section of SoloLearn?

Question

What is the output of this code?

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

The answer was 7 but I need some help understanding why?

Thanks!

Answer 1

x+=x is the same as x = x + x.
So,
x = 1
x = 1 + 1
x++ , now x is 3
x = 3 + 3
x++ , x is now 7
x < 5 is now false, loop ends.

Answer 2

Thank you!! That makes sense now :)