JavaScript TypeError – Reduce of empty array with no initial value

This JavaScript exception reduce of empty array with no initial value occurs if a reduce function is used with the empty array.

Message:

TypeError: reduce of empty array with no initial value

Error Type:

TypeError

Cause of Error:

This error is raised if an empty array is provided to the reduce() method because no initial value can be returned in this case.

Example 1: In this example, the filter method removes all elements, So the reduce method applies to empty array and error occurred.

Javascript

let arr = [1, 2, 3, 4, 5, 6];
arr.filter(x => x < 0)
    // This removes all elements
    .reduce((x, y) => x * y) // TypeError

Output(in console):

TypeError: reduce of empty array with no initial value

Example 2: In this example, there is an unexpected number of elements in a list, Which could cause a problem.

Javascript

let classNm = document.getElementsByClassName("ClassName");
let GFG_list =
    Array.prototype.reduce.call(classNm, (a, b) => a + ": " + b);

Output(in console):

TypeError: reduce of empty array with no initial value