I have written the following loop:
for (i = 10; i--; i > 5) {
console.log(i);
}
Which outputs this to the console:
9
8
7
6
5
4
3
2
1
0
Can anyone tell me why it's doing this?
I had a look and it seems like it's just a simple matter of having to increment using the third parameter of the for loop, rather than the second, but I'm fascinated as to the digits logged to the console. Can anyone give me a simple explanation of why it outputs the numbers it does?
The for loop has this structure:
for (initial condition ; termination condition ; incremental condition)
In your for loop, the termination and incremental condition are swapped (!):
for (i = 10; i--; i > 5)
That is:
initial condition: i = 10
termination condition: i-- !!!
incremental condition: i > 5 ??? Does not do incremental
Then, as long as the termination condition returns true (that is, when i > 0), the loop continues.
And since i, having an initial value of 10, will only become 0 after the i-- is executed 10 times, the result returned was:
9 8 7 6 5 4 3 2 1 0
Totaling 10 loops.
i-- which causes it to act differently from what might appear to be its intended purpose? That is: why does i-- function as one might expect i > 0 to in this particular context? In what manner is the lower level processing involved similar?
var me = "Reads above data with increasing fascination."The loop did not finish when you expected because Boolean(i--) is false only if i == 0; in short, you misplace compare and action in the loop.
i-- performing at the level below the visible level, causing Boolean(i--) to return true when i == 0? Also, why is it not i <= 0? Also, given i > 5 shouldn't be an incremental condition at all, why is the loop incrementing by one step?
i-- produces digits, 9876543210, as i-- is placed on condition place it checking if result of i-- is true, so, long story is short, it happens only when i eq zero. i>5 does not change i, and so, not affecting the loop.Question is now corrected so ignore: Firstly, you are wrong - it does not produce the output you indicated :). Instead it produces the following:
for (i = 11; i--; i > 5) {console.log(i);}
// 10 9 8 7 6 5 4 3 2 1 0
It starts with 10, not with 9 :).
Secondly, you are not allowed to change the order of statements in the for block. Instead, you must specify them as shown:
for (i = 11; i > 5; i--) { console.log(i); }
// 11 10 9 8 7 6
Third (and most important):
i; whatever value you want or need.i.
