What is the Difference Between JavaScript Array.reduce() and Array.reduceRight() in JavaScript

In JavaScript,
the difference between Array.prototype.reduce() and Array.prototype.reduceRight() methods is how they traverse elements of an array:

• Array.prototype.reduce() starts from left-to-right;
• Array.prototype.reduceRight() starts from right-to-left.

Here is an example, which illustrates the difference between the two:

const arr = ['a', 'b', 'c', 'd'];

const ltr = arr.reduce((previous, current) => previous + current);
const rtl = arr.reduceRight((previous, current) => previous + current);

console.log(ltr); // 'abcd'
console.log(rtl); // 'dcba'