JS-ES6 Cheatsheet Promises

promises.js

//Promise.all
//Devuelve todas las promesas o el primer reject que ocurra
//***********************************************************************************/
const names = ["Victoria", "Ivan", "Katya", "Lina", "Jack"];

//Promise declaration
const returnAfter1sec = (value) => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            resolve(value);
        }, 1000);
    });
}


let promises = names.map((a) => returnAfter1sec(a)); //Array of promises

let data = Promise.all(promises); //Promise

//Resolve it with then
data.then((result) => {
    console.log(result);
}).catch((err) => {
    console.log(err);
});

//Or 
let result = await Promise.all(promises);
console.log(result);


//Promise.any
//Devuelve la promesa ganadoraa, ignora los reject
//***********************************************************************************/
const returnAfterTime = (time, value) => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {                 
            resolve(value);
        }, time * 1000);
    });
}

const rejectAfterTime = (time, value) => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {                 
            reject(new Error(value));
        }, time * 1000);
    });
}


let promises = [];

promises.push(returnAfterTime(1, "Promise 1"));
promises.push(returnAfterTime(0.5, "Promise 2"));
promises.push(rejectAfterTime(0.25, "Promise 3"));
promises.push(returnAfterTime(3, "Promise 4"));
promises.push(returnAfterTime(5, "Promise 5"));

let data = Promise.any(promises); 

data.then((result,error) => {
    error ? console.log(`Rejected with  ${error}`) : console.log(`Fulfilled with  ${result}`);       
}).catch((err) => {
    console.log(err);
});
//Output : Fulfilled with  Promise 2



//Promise.race
//Devuelve la promesa que se resuelva o rejecte primero
//***********************************************************************************/
const returnAfterTime = (time, value) => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {                 
            resolve(value);
        }, time * 1000);
    });
}

const rejectAfterTime = (time, value) => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {                 
            reject(new Error(value));
        }, time * 1000);
    });
}


let promises = [];

promises.push(returnAfterTime(1, "Promise 1"));
promises.push(returnAfterTime(0.5, "Promise 2"));
promises.push(rejectAfterTime(0.25, "Promise 3"));
promises.push(returnAfterTime(3, "Promise 4"));
promises.push(returnAfterTime(5, "Promise 5"));

let data = Promise.race(promises); 

data.then((result,error) => {
    error ? console.log(`Rejected with  ${error}`) : console.log(`Fulfilled with  ${result}`);       
}).catch((err) => {
    console.log(err);
});
//Output : Error: Promise 3

//Promise.allSettled
//Devuelve todos los resultados ya sean resolved o rejected
//***********************************************************************************/
const returnAfterTime = (time, value) => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            resolve(value);
        }, time * 1000);
    });
}

const rejectAfterTime = (time, value) => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            reject(new Error(value));
        }, time * 1000);
    });
}


let promises = [];

promises.push(returnAfterTime(1, "Promise 1"));
promises.push(returnAfterTime(0.5, "Promise 2"));
promises.push(rejectAfterTime(0.25, "Promise 3"));
promises.push(returnAfterTime(3, "Promise 4"));
promises.push(returnAfterTime(5, "Promise 5"));

let data = Promise.allSettled(promises);

data.then((result) => {
    result.map(p => p.reason ? 
        console.log(`Rejected with   ${p.reason}`) : 
        console.log(`Fulfilled with  ${p.value}`)
    )
}).catch((err) => {
    console.log(err);
});



// El metodo async siempre retorna una promesa
// no necesitas hacer resolve si ya estas esperando una promesa

var fetch = require('request-promise');

var url = 'https://jsonplaceholder.typicode.com/todos/1';
const callAPI = async (time) => {
    var html = await fetch(url);  
    return html;
}

const main = async () => {   
    var x = await callAPI(5);
    console.log(x);
}

main();



//Metodo Promise.prototype.finally
promise
    .then(result => {
        // process the result
    })
    .catch(error => {
        // handle the error
    })
    .finally(() => {
        // clean up the resources
    });