// ES6
// a
let a = text => alert(text);

// cube
let cube = (a) => a * a * a;

// avg2
let avg2 = (a, b) => (a + b) / 2;

// sum3
let sum3 = (a = 0, b = 0, c = 0) => a + b + c; 

// intRandom
let intRandom = (a = 0, b = 0) => Math.round(Math.random() * (b - a)) + a;

// greetAll
let greetAll = (...arguments) => {
    for (let i in arguments) {
        alert('"' + 'Hello' + ' ' + arguments[i] + '"');
    }
}

// sum
let sum = (...arguments) => {
    let sum = 0;
    for (let i = 0; i < arguments.length;i++) {
        sum += arguments[i];
    }
    return sum;
}

// sort
function byField(field, order) {
    let collator = new Intl.Collator(["en", "ru"], {
        numeric: true
    })
    order = order ? 1 : -1;
    return function(a, b) {
        return order * collator.compare(a[field], b[field]);
    }
}

let users = [{
    name: "Иван",
    age: 17,
}, {
    name: "Мария",
    age: 35,
}, {
    name: "Алексей",
    age: 73,
}, {
    name: "Яков",
    age: 12,
}]

users.sort(byField('age', true));  //сортирует по возрасту по возрастанию
users.sort(byField('name', true)); //сортирует по имени по убыванию

// array map
let Array = ["1", {}, null, undefined, "500", 700];

let result  = Array.map(function(item) {
    let number = parseInt(item);
  return isNaN(number)? item : number;
})

console.log(result);

// array reduce
let arr = ["0", 5, 3, "string", null];
let result = arr.reduce(function(previousValue, currentValue) {
return typeof currentValue == 'number' ? previousValue * currentValue : previousValue;
},1);
console.log(result);

// object filter
function filter(obj, callback) {
    let mainObj = {};
        for(let key in obj) {
            if (callback(key, obj[key])) {
                mainObj[key] = obj[key];
            }
        }
        return mainObj;
    }

    let phone = {
        brand: "meizu",
        model: "m2",
        ram: 2,
        color: "black",
    }

let outcome = filter(phone,(key,value) => key == "color" || value == 2);
console.log(outcome);

// object map
function map(object, callback) {
    let obj = {};
        for(let key in object)
        Object.assign(obj,callback(key, object[key]));
        return obj;
    }
    let obj = map({name: 'Иван', age: 17}, function(key, value) {
        let result = {};
        result[key+"_"] = value + "$";
        return result;
    })

console.log(obj);
//возвращает {name_: "Иван$", age_: "17$"}

// Sum
// pешение с помощью цикла
function sum(n) {
    let	sum = 0;
    for (let i = 1;i <= n;i++) {
        sum += i;
    }
    return sum;
}

// or
// pешение через рекурсию
function sum(n) {
    if (n == 1) return 1;
    return n + sumTo(n - 1);
}