flattened-javascript-promise-chains.js

//--------------------------------------------------------------------
// http://solutionoptimist.com/2013/12/27/javascript-promise-chains-2/                                
//--------------------------------------------------------------------

//--------------------------------------------------------------------
// Pretend calls to a service
//--------------------------------------------------------------------
function getDeparture() {                                                                             
    return new Promise((resolve) => {
        setTimeout(function() {                                                                       
            resolve('chicago');
        }, 1000);                                                                                     
    });                                                                                               
}                                                                                                     

function getFlight(departure) {                                                                       
    return new Promise((resolve) => {                                                                 
        setTimeout(function() {                                                                       
            resolve(departure + ' - flight 999');                                                     
        }, 1500);
    });
}   

//--------------------------------------------------------------------
// Anti pattern...
//--------------------------------------------------------------------
getDeparture().then(departure => {                       
    getFlight(departure).then(flight => {                                                             
        console.log(flight);
    })
});

//--------------------------------------------------------------------
// Decent, but has tedious promise handlers
//--------------------------------------------------------------------
getDeparture().then(departure => {
    return getFlight(departure);
}).then(flight => {
    console.log(flight);    
});

//--------------------------------------------------------------------
// The money version
//--------------------------------------------------------------------
function fetchDeparture() {
    return getDeparture().then((departure) => {
        return departure;
    });
}

function fetchFlight(departure) {
    return getFlight(departure).then((flight) => {
        console.log(flight);
    });
}

fetchDeparture().then(fetchFlight);