Javascript Array Length

Number Of Elements

length // prints 0 empty array The dense array does not have empties and the number of items corresponds to Length as a number bigger than highest index is greater than the highest index but it does not indicate the real number of elements

Does Not

length3 But the sparse array does not have an element at index 0

Output

This allows you to react differently depending on whether iterating finished successfully something that is slightly tricky with Transformation methods take an input array and produce an output array while the callback controls how the output is produced

Not Have