reduce.js

const data = [1,3,4,5];
const rta = data.reduce((counter, item) => counter + item, 0);
console.log(rta);

const orders = [
  {
    customerName: 'Nicolas',
    total: 60,
    delivered: true,
  },
  {
    customerName: 'Zulema',
    total: 120,
    delivered: false,
  },
  {
    customerName: 'Santiago',
    total: 180,
    delivered: true,
  },
  {
    customerName: 'Valentina',
    total: 240,
    delivered: true,
  },
];

const rta = data
.map(item => item.total)
.reduce((counter, item) => counter + item, 0);
console.log(rta);

const data = [
  {
    name: 'Nicolas',
    level: 'low'
  },
  {
    name: 'Andrea',
    level: 'medium'
  },
  {
    name: 'Zulema',
    level: 'hight'
  },
  {
    name: 'Santiago',
    level: 'low'
  },
  {
    name: 'Valentina',
    level: 'medium'
  },
  {
    name: 'Lucia',
    level: 'hight'
  }
]

const rta = exams
.map(item => item.level)
.reduce((rta, item) => {
  if(rta[item]) {
    rta[item] = rta[item] + 1;
  } else {
    rta[item] = 1;
  }
  return rta;
}, {})

const matriz = [
  [1,2,3],
  [4,5,6],
  [7,8,9]
];

const rta = matriz.reduce((rta, item)=> {
  return [...rta, ...item];
}, []);

const rta1 = matriz.flat();