keyvan-m-sadeghi

const states = {
    pending: 'Pending',
    resolved: 'Resolved',
    rejected: 'Rejected'
};

keyvan-m-sadeghi

class Nancy {
    constructor(executor) {
        const resolve = () => {
            this.state = states.resolved;
        };

        const reject = () => {
            this.state = states.rejected;
        };

keyvan-m-sadeghi

const getCallback = state => value => {
    this.value = value;
    this.state = state;
};

const resolve = getCallback(states.resolved);
const reject = getCallback(states.rejected);

keyvan-m-sadeghi

class Nancy {
    constructor(executor) {
        const members = {
            [states.resolved]: {
                state: states.resolved,
                // Chain mechanism
                then: onResolved => Nancy.resolve(onResolved(this.value))
            },
            [states.rejected]: {
                state: states.rejected,

keyvan-m-sadeghi

class Nancy {
    ...
    static resolve(value) {
        return new Nancy(resolve => resolve(value));
    }

    static reject(value) {
        return new Nancy((_, reject) => reject(value));
    }
}

keyvan-m-sadeghi

let p = new Nancy((resolve, reject) => {
    resolve(42);
    reject(24); // ignored
    resolve(); // ignored
});

p
    .then(value => Nancy.reject(value)) // rejects
    .catch(value => console.log(value)); // logs 42

keyvan-m-sadeghi

const delay = milliseconds => new Nancy(resolve => setTimeout(resolve, milliseconds));
const logThenDelay = milliseconds => total => {
    console.log(`${total / 1000.0} seconds!`);
    return delay(milliseconds)
        .then(() => total + milliseconds);
};

logThenDelay(500)(0) // logs 0 seconds!
    .then(logThenDelay(500)) // after 0.5 seconds, logs 0.5 seconds!
    .then(logThenDelay(500)) // after 1 second, logs 1 seconds!

keyvan-m-sadeghi

class Nancy {
    constructor(executor) {
        const tryCall = callback => Nancy.try(() => callback(this.value));
        const members = {
            [states.resolved]: {
                ...
                then: trycall
            },
            ...
        };

keyvan-m-sadeghi

const anything = () => {
    throw new Error('I can be anything because I should never get called!');
};
const throwSomethingWrong = () => {
    console.log('not ignored!');
    throw new Error('Something went wrong...');
};

const p = Nancy.reject(42)
    .catch(value => value) // resolves

keyvan-m-sadeghi

[states.resolved]: {
    ...
    then: tryCall,
    catch: _ => this
},
[states.rejected]: {
    ...
    then: _ => this,
    catch: tryCall
}