Javascript: reduce()

The reduce() method executes a reducer function on each element of the array.

### Syntax

arr.reduce(callback( accumulator, currentValue, [, index[, array]] )[, initialValue])

### example

const numbers = [3, 5, 8, 9, 12];
const total = numbers.reduce((accumulator, currentValue) => accumulator + currentValue, 0);
console.log(total);
// 37

### To set a initialValue

const numbers = [3, 5, 8, 9, 12];
const result = numbers.reduce((accumulator, currentValue) => accumulator + currentValue, 3);
console.log(result);
// 40

### another one example for to set a initialValue

const numbers = [3, 5, 8, 9, 12];
const result = numbers.reduce((accumulator, currentValue) => accumulator - currentValue, 40);
console.log(result);
// 3

### here is details of every step changes value

const numbers = [3, 5, 8, 9, 12];
const result = numbers.reduce((accumulator, currentValue) => {
    console.log(accumulator, currentValue);
    return accumulator + currentValue;
 }, 0);
console.log('Result: ', result);
// 0 3
// 3 5
// 8 8
// 16 9
// 25 12
// 25 12

### reduce method apply on a object of array

const employeeList = [
    {
      name: 'Piter',       
      salary: 1200
    },
    { 
        name: 'Harry',
         salary: 1500
    },
    {
        name: 'Mark',
        salary: 1800
    }
 ];
const totalSalary = employeeList.reduce((sum, employee) => sum + employee.salary, 0);
console.log(totalSalary);
// 4500