JS reduce

JS reduce

·

1 min read

  1. Returns single value.
  2. Doesn't mutate original array.
  3. Doesn't execute the function for empty array elements.
  4. Syntax: array.reduce(function(previousValue, currentValue, currentIndex, arr), initialValue);

reduce1.jpeg

previousValue: value resulting from the previous call to callBackFn. On first call, initialValue if specified otherwise array[0].

currentValue: value of the current element.On the first call, the value of array[0] if initialValue specified otherwise array[1].

currentIndex: currentValue index. On first call it is 0 if initialValue specified otherwise 1.

reduce2.jpeg

Examples

reduce3.jpeg


reduce4.jpeg


reduce5.jpeg


Functional Composition:

reduce6.jpeg

In above, example input is function returned by (...functions) as we are calling multiply6(6). Hence input is 6.

Reference: MDN official

Thank you. :)