Not completely understanding the for loop function call of (lis[i]);

Question

Just need some help breaking down the for loop of the code. I am not quite understanding the function call of (lis[i]);
for (let i = 0; i < lis.length; i +=1) {
  attachListItemButtons(lis[i]);
}

Peter Vann · Answer

Considering this code:
javascript
for (let i = 0; i < lis.length; i += 1) {
    attachListItemButtons(lis[i]);
}

I'm not sure exactly what the function attachListItemButtons() does, but lis appears to be an array.
Therefore, the loop is passing the value in each successive ordinal position in the array to the function attachListItemButtons() on each iteration of the loop.
In other words, if the array is:
javascript
const lis = [1, 2, 3];

then the loop, in effect would be doing this:
javascript
attachListItemButtons( 1 );
attachListItemButtons( 2 );
attachListItemButtons( 3 );

because the loop flow would be:
javascript
lis[i] == 1;
lis[i] == 2;
lis[i] == 3;

which is really:
javascript
lis[0] == 1;
lis[1] == 2;
lis[2] == 3;

One way to really see it is to code it this way:
javascript
for (let i = 0; i < lis.length; i += 1) {
    console.log(lis[i]);
    attachListItemButtons(lis[i]);
}

And look at the console output in devtools on your browser (or command line if using node).
Does that answer your question?
I hope that helps.
Stay safe and happy coding!

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David Holt

David Holt

Not completely understanding the for loop function call of (lis[i]);

1 Answer

Peter Vann

Peter Vann