💩Array.reduce()

.reduce

no mutation

Description

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

Array.prototype.reduce ( callbackfn [ , initialValue ] )

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce

Example

const array1 = [1, 2, 3, 4];
const reducer = (accumulator, currentValue) => accumulator + currentValue;

// 1 + 2 + 3 + 4
console.log(array1.reduce(reducer));
// expected output: 10

// 5 + 1 + 2 + 3 + 4
console.log(array1.reduce(reducer, 5));
// expected output: 15

reduce()

const array = [1, 2, 3, 4]const result = array.reduce((accumulator, current) => (   accumulator + current), 10)// array = [1, 2, 3, 4]// result = 20

reduce method will take in reducer function and initial value as arguments. The reducer function can take up to 4 arguments: accumulator, element, index, and array. The reducer function will be executed for each iteration and the returned value of each iteration will be used for the next iteration.

Note: reduce method returns a single value not an array.