Основы

Types#

Просмотреть видео ниже. После каждой под-темы ставить видео на паузу и повторять набранный лектором код.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>JavaScript Intro</title>
</head>
<body>
    <script>
        let alex;
​
        class Contact {
            constructor(fistNameOrObject, lastName, email) {
                if (typeof fistNameOrObject === 'object') {
                    Object.assign(this, fistNameOrObject);
                } else {
                    this.fistName = fistNameOrObject;
                    this.lastName = lastName;
                    this.email = email;
                }
            }
​
            toString() {
                return `${this.fistName} ${this.lastName} <${this.email}>`;
            }
        }
​
        alex = new Contact('Alex', 'Kotov', 'alexko@in6k.com');
        console.log('in main', '' + alex);
​
        let vladik = new Contact({
            fistName: 'Vladik', 
            lastName: 'Nikolenko',
            email: 'vladik@in6k.com',
        });
        console.log('in main', '' + vladik);
​
        let colors = { red: '#ff0000', blank: '#000000', white: '#ffffff' };
        for (let name in colors) {
            console.log(name + ' has code ' + colors[name].toUpperCase());
        }
    </script>
</body>
</html>

var vs let vs const#

Debugging#

https://code.visualstudio.com/docs/nodejs/nodejs-debugging

Branches and loops#

0 of 3

💻 Функция плюаризации слова. Сделать для всех случаев: 0, 2-4, 5-10, 11-19, 20-99, 100 и больше
💻 Функция подсчета суммы в диапазоне целых чисел
💻 Функция подсчета факториала до заданного элемента

Typical issues#

no return fn sum(a, b) { return a + b; } command query separation principle
global variables var result = ''; fn(s) { result += s;}
extra code return age >= 18 ? true : false;
big complex if

if(count === 0 ||  count <=20 && count >= 5 || count % 10 === 0 || count % 10 <=19 && count % 10 >= 5 || count % 100 == 20){
    return count + ' ' + many;
}

code formatting

function plural(count, one, few, many) {
    if(count%10 == 1 && count%100 != 11){
                return (count+" "+one);
            }else if (count%100 == 11 || count%10 === 0  || 5<=count%10 && count%10<=9){
                return(count+" "+many);
            }else{
                return(count+" "+few);
            }
}

code duplication

    if (11 <= count && count <= 14) return count +' ' + many;
    ----11---------count---------19------------->
    
    if (count === 11) 
    if (count === 12) return count +' ' + many;
    if (count === 13) return count +' ' + many;
    if (count === 14) return count +' ' + many;

naming dob, suma: better to use result
"рычащие" название переменных

let newarr =  [...arr]
let words = newarr.slice(1, 4)