Javascript change for loop variable from within the loop

Question

I have a for loop like so

for (var i = 0; i < 100; i += 4) {
    // code with i;
}

I would like to change the value of i to a certain value from within the loop. I am aware you could use continue to change the value of i after evaluating the final-expression, but what if I wanted to change the value of i to something more specific like 40?

Here's one of my attempts

loop:
for (var i = 0; i < 100; i += 4) {
    for (var i = 0; i <= 40; i++) {
        continue loop;
    }
}

Is there a better way of doing this?

Why can't you just assign it the value you want? It's just another variable after all. Just make sure you don't set it in such a way that you'll infinitely loop. — cookie monster, Jan 01 '14 at 21:03
I see that I could've reassigned it now. And yes this is one question I'm looking an answer to in order to solve a bigger problem. — Patrick, Jan 01 '14 at 21:23

score 3 · Accepted Answer · answered Jan 01 '14 at 21:03

3

Just change i directly:

for (var i = 0; i < 100; i += 4) {
    i = 15000;
}

This would exit the loop immediately, but you could do whatever you wanted.

You should read up on function scope to understand how this stuff works. For loops are bit different from functions in that they're a language construct but the same theory of scope holds true.

answered Jan 01 '14 at 21:03

dudewad

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I don't want to exit the loop after I change the i value though. Is there another way of doing this? I'll go read function scope and look. – Patrick Jan 01 '14 at 21:17
2

nvm I see why it would exit the loop imeediately. Because 15000 < 100. – Patrick Jan 01 '14 at 21:19

Rohit Agrawal · Answer 2 · 2014-01-01T21:15:42.523

1

The scope of increment variable is always available inside the loop block, this allows you to access increment variable inside the loop block.

for (var i = 0; i < 100; i += 4) {
    if (condition)  i = 40 ;
    /* put any condition to avoid the infinite loop and continue with your rest of code */
}

edited Jan 01 '14 at 21:15

answered Jan 01 '14 at 21:06

Rohit Agrawal

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You should add some condition to avoid the infinite loop, – cookie monster Jan 01 '14 at 21:06
@cookiemonster definitely this will not be the complete loop he must be doing something inside the loop – Rohit Agrawal Jan 01 '14 at 21:07
Yeah, just wanted to make sure that some beginner out there didn't run the code and freeze their browser. ;-) – cookie monster Jan 01 '14 at 21:08
Yea I'm doing something else within the loop, but I just got stuck on this part. – Patrick Jan 01 '14 at 21:16
1

share your complete loop and tell us what you want to do – Rohit Agrawal Jan 01 '14 at 21:16
I would put everything up, but I'm solving a puzzle atm and think it would be too long and a new topic onto itself. – Patrick Jan 01 '14 at 21:53

Javascript change for loop variable from within the loop

2 Answers2