Question

I cam across the following function in javascript:

for (var number = 0; number <= 12; number = number + 2)
  show(number);

The Output is the following

0
2
4
6
8
10
12

I expected it to be

2
4
6
8
10
12
14

Why is the “0” shown first and not “2” since the “number = number + 2″comes before the “show(number);”?

Answer 1

This because the order of the loop is like this:

1. Init number.
2. Check the condition.
3. Run the loop.
4. Increase number by 2.

and then 2-4 again until the condition is false, if so exits the loop.

the for loop translate to something like this:

var number = 0;
while (number <= 12)
{
  show(number);
  number = number + 2;
}

In general for loop always work like this:

for(Init Variable; Condition ; Changing Variable)
{
   //Some Code
}

translates to:

Init Variable
while (Condition )
{
  //Some Code

  Changing Variable
}