here's my code:
<script>
for (j = 0 ; j < 17 ; ++j)
{
x = j
document.write(x)
document.write(' ')
document.write(j)
document.write('<br />')
}
</script>

I do not understand why I get 0 0 on the first line of my html page when i am asking the for loop to pre increment j. Can anyone help me understand? I appreciate it!!!

If memory serves with my looping mechanisms, while you have the loop condition set up to a pre-increment, the for loop won't evaluate the incrementing statement (++j) until after the first time the loop has run.

If you do want to update your value before processing the, what you need to use is a while loop, since it evaluates the condition before actually performing the details in the loop. When updated, it looks like this:



Now the big trick (I'm not sure if you're trying to do this or not) to having "chasing" values is to increment the x value at the end of your while loop:



Hope this helps!

thanks!

To explain your first statement to help in the future

If you set j=1 in your first statement that would give you a start of 1.

You get 0 0 as a result due to this:
document.write(x) = 0 because J= 0 and you are saying x = j
document.write(' ') one space
document.write(j)= 0 as set
if J were set to 1 initially it would be 1 1
Programming employs the rules of algebra and applies to all programming languages.

Prism - just to be clear, I wasn't questioning basic algebra.

I was questioning why the preincrement ++j does not preincrement.

There is no difference in the behavior of a for loop whether i preincrement with a ++j or post increment with a j++ as far as I can tell.

Why should it you have told the expression to start with zero so x also equals 0
The important part is you have said start with a value of j = 0 then the next time round increment j by 1

for (j = 0 ; j < 17 ; ++j)
{
x = j

If j= 1 then the starting value would be 1. Nothing to do with the increment until it reiterates. Read my explanation again you are asking the value of j to be 0 and that is what you get.

Or
s = 1 The starting value or whatever you want it to be. It will be that value until it loops
for(j=s;j<17;++j)

++ is not a pre increment it is just an increment

i'm not sure why you say ++j is not a pre increment. in any chunk of code other than a for loop, it is absolutely a pre increment, and j++ is a post increment. They do different things.

Php is similar to Javascript I changed the variables to conform and 5 instead of 17 to keep the progression small

Result :- 0 0 1 1 2 2 3 3 4 4
Changing the increment to $j++

Result :- 0 0 1 1 2 2 3 3 4 4
Changing the value of $j=1


Result :- 1 1 2 2 3 3 4 4

I completely agree. That is all true. That is exactly what I said.