I am having trouble understanding this code. I get 10 as the answer, not 7. Can someone please explain?

Question

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

Answer 1

x=1.
for x<5 true
x=x+x=1+1=2
x++ =>x=x+1=3

3<5 true
x=x+x=3+3=6
x++ =>x=7

7<5 false.
Alerts 7

So 7 only not 10...
You may missing something in code if you got as 10..

Answer 2

format of if statement is:

if (
<statement_to_be_ran_once_at_sart :: initialization (usually init of counter variable)>;
<condition_evaluated_at_end_of_each_iteration :: if false quit the loop>;
<statement_to_be_executed_at_end_of_each_iteration :: usually counter incrementation>
) {
<code_executed_at_each_iteration>
}

Anyway, it's totally valid to have one to all of this fourth part empty... for dumb example this work, even if infinite loop doing absolutly nothing:

for (;;);

(curly braces can be avoided if only one statement inside it -- could be many expressions comma "," separated -- but all semi-colons ";" are mandatory)

Answer 3

My mistake was that I was incrementing before I executed the code in the curly brackets.