js4online_homework/08/main.js

// sort
var persons = [
   { name: "Иван", age: 17 },
   { name: "Мария", age: 35 },
   { name: "Алексей", age: 73 },
   { name: "Яков", age: 12 },
]
function sort(persons, key, ok = true) {
   return persons.sort((a, b) => {
      let result;
      if (ok) { result = a[key] > b[key] ? 1 : -1; }
      else { result = a[key] < b[key] ? 1 : -1; }
      return result;
   })
}
console.log(sort(persons, "age"));
///////////////////////////////////////////////
console.log(sort(persons, "name", false));
///////////////////////////////////////////////
console.log(sort(persons, "name"));

// array map
var numbers = ["1", {}, null, undefined, "500", 700].map(function (a) { if ((+a) > 0) return +a; else return a })
console.log(numbers)

// array reduce
let number01 = ["0", 5, 3, "string", null];
let number02 = number01.filter(item => typeof item === 'number').reduce((a, b) => a * b)
console.log(number02)

// object filter
var phone = {
   brand: "meizu",
   model: "m2",
   ram: 2,
   color: "black",
};
function filter(object, callback) {
   let filterPhone = {}
   for (let key in object) {
      if (callback(key, object[key]))
         filterPhone = { ...filterPhone, [key]: object[key] };
   }
   return filterPhone;
}
console.log(filter(phone, (key, value) => key == "color" || value == 2));

// object map
function objectMap(object, callback) {
   let filter = {}
   for (let key in object) {
      filter = { ...filter, ...callback([key], object[key]) };
   }
   return filter;
}
let finish = objectMap({ name: "Иван", age: 17 }, function (key, value) {
   var result = {};
   result[key + "_"] = value + "$";
   return result;
})
console.log(finish)

// Рекурсия
// Sum
let fact = n => n <= 0 ? 0 : n + fact(n - 1);
console.log(fact(0))
console.log(fact(1))
console.log(fact(3))
console.log(fact(5))
console.log(fact(7))
console.log(fact(9))