Promises and generators examples for Jeff

promises_and_generators_ examples.js

const co = require('co');

// Asynchronous examples

// Callback function
setTimeout(() => {
    console.log('This is a callback function!');
}, 100);

// Promise-returning function example
const promiseReturningFunc = name => {
    return new Promise((resolve, reject) => {

        setTimeout(() => {
            resolve(name);
        }, 100);

    });
};

{
    // const name = promiseReturningFunc('Ryan');

    // This won't work, because name will be a Promise, not a value
    console.log(name);

    // This will work
    promiseReturningFunc('Ryan')
        .then(name => {
            console.log(name);
        })
        .catch(err => {
            console.error(err);
        });
}

co(function*() {
    try {

        const names = ['Ryan', 'Hannah Joy', 'Rand'];

        // const name = yield promiseReturningFunc('Ryan');

        // console.log(name);

        for (const n of names) {
            const name = yield promiseReturningFunc(n);
            console.log(name);
        }

    } catch (err) {
        console.error(err);
    }
});

//example of promise-returning function with generator internally
const convert = () => {
    return new Promise((resolve, reject) => {
        co(function*() {
            try {

                const name = yield promiseReturningFunc('Ryan');
                resolve();

            } catch (err) {
                reject(err);
            }
        });
    });
};