If the loop variable of a for loop ranges over the indices of an array, that variable
would normally be used as an array index in the body of the loop. If, instead, the loop body only
refers to array elements at constant indices, this may indicate a logic error or leftover testing
code.
Examine the loop carefully to ensure it is behaving as expected. You may want to consider using
a for-of loop to iterate over all elements of an array without the need
for error-prone index manipulations.
The following example shows a function that is intended to sum up the elements of an array
xs. The loop variable i is counted up from zero to
xs.length-1, but instead of adding xs[i] to the running sum
res, the code adds xs[0], the first element of xs,
to it, which is likely a mistake:
The problem can be fixed by adding xs[i] instead:
Alternatively, the function can be written more succinctly using a for-of
loop: