JavaScript Array reduce Method (Live Playground)

The reduce method in JavaScript applies a function against an accumulator and each element in the array (from left to right) to reduce it to a single value.

Here's an example:

let numbers = [1, 2, 3, 4, 5];

let sum = numbers.reduce(function (total, number) {
  return total + number;
}, 0);

console.log(sum);
// Expected output: 15

In this example, numbers.reduce(function(total, number) { return total + number; }, 0) returns the sum of all elements in the numbers array. The number 0 passed as the second argument to reduce is the initial value for the total.

Live Playground, Try it Yourself

The reduce method does not change the original array. For example, if we console.log the numbers array, we will see that it stays the same:

console.log(numbers);
// Expected output: [1, 2, 3, 4, 5]

Live Playground, Try it Yourself

The reduce method is useful when you need to process an array's elements into a single value, such as summing numbers or finding a product.

Always practice the reduce method with different scenarios to improve your understanding!