js async examples

// 0 - synchronios call
function runSync() {
    const end = Date.now() + 3000;
    while (Date.now() < end) {
        const doSomethingHeavyInJavaScript = Math.random;
    }
    return 'task done';
}

console.log('1');
console.log(runSync());
console.log('2');

//     async
// 1 - callback
function runAsync(data, callback) {
    setTimeout(() => callback('task done'), 3000);
}

console.log('1');
runAsync({}, (result) => console.log(result));
console.log('2');
// 3.5 callback hell
// todo

// 2 - promise
let promise = new Promise(
    (resolve, reject) => {
        setTimeout(() => resolve('ok'), 3000);
    }
)

let promiseReject = new Promise(
    (resolve, reject) => {
        setTimeout(() => reject('something not worked'), 3000);
    }
)

console.log('1');
promise
    .then(
        result => {
            console.log(result);
        }
    )
    .then(() => promiseReject)
    .catch(error => {
        console.log(error);
        throw error;
    })
console.log('2');

// promise chaining
// todo

// 3 - async/await
let promise = new Promise(
    (resolve, reject) => {
        setTimeout(() => resolve('ok'), 3000);
    }
)

async function run() {
    console.log('1');
    let result = await promise;
    console.log(result);
    console.log('2');
}
run();
// 4 - rxjs
// todo