Javascript for loop missing middle part: error or advanced?

Question

I am in the process of debugging another developer's Javascript for a project at work.

I am probably a mid-level Javascript developer on a good day and I've come across a for loop that appears broken:

for(i = 0; ; i++)

Can anyone tell me if this is indeed a mistake or if in some instances this is a perfectly valid way to do Advanced things?

Answer 1

It's OK and perfectly legal. Any of the three slots in a for statement can be left empty. Except for the condition that i added, it's logically the same as this:

i = 0;
while (true) {
    // other code here
    if (some condition) {
        break;
    }
    i++;
}

It will be an infinite loop unless there is a test somewhere in the loop that issues a break statement under some conditions to stop the loop (I added a sample test to my code example).