[SOLVED] Javascript – Loop two arrays inside another functional way

Issue

I have two arrays vehicles and routes, given below

const vehicles = [{ name: 'TukTuk', maxSpeed: 12 },
{ name: 'Bike', maxSpeed: 10 },
{ name: 'Car', maxSpeed: 20 }];

const routes = [{ name: 'routeOne' , distance: 18, allowedSpeed: 12 }
, {name: 'routeTwo',  distance: 20, allowedSpeed: 10 }];

There is this rule, the vehicle would travel in the route’s allowed speed even it can ride faster

That is covered written in this function

const getTravelTime = (vehicle, route) => { 
    return route.allowedSpeed < vehicle.maxSpeed ? (route.distance / route.allowedSpeed) : (route.distance / vehicle.maxSpeed);
};

The objective is to find the fastest route and vehicle for the Journey

I have a implementation which is not functional

const getFastestJourney = (vehicles,routes) => {
    let fastestTime = Infinity; 
    let fastestRoute,fastestVehicle;
    for(let i =0;i < vehicles.length; i++){
        for(let j=0;j< routes.length;j++){
            let travelTime = getTravelTime(vehicles[i],routes[j]);
            if(travelTime < fastestTime){
                fastestVehicle = vehicles[i];
                fastestRoute = routes[j];
                fastestTime = travelTime;
            }
        }
    }
    return {
        route: fastestRoute,
        vehicle: fastestVehicle,
    };
};

how do I achieve that in the functional way?

Solution

You could get an array of all combinations of vehicles and routes and their travel time and reduce this array by looking for shorter time and faster vehicle.

const
    vehicles = [{ name: 'TukTuk', maxSpeed: 12 }, { name: 'Bike', maxSpeed: 10 }, { name: 'Car', maxSpeed: 20 }],
    routes = [{ name: 'routeOne' , distance: 18, allowedSpeed: 12 }, {name: 'routeTwo',  distance: 20, allowedSpeed: 10 }],
    getTravelTime = (vehicle, route) => route.distance / (route.allowedSpeed < vehicle.maxSpeed ? route.allowedSpeed : vehicle.maxSpeed),
    result = vehicles
        .flatMap(v => routes.map(r => ({ 
            vehicle: v.name,
            maxSpeed: v.maxSpeed,
            route: r.name,
            time: getTravelTime (v, r)
        })))
        .reduce((a, b) => 
            a.time === b.time && a.maxSpeed > b.maxSpeed ||
            a.time < b.time
                ? a
                : b
        );

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answered By – Nina Scholz

Answer Checked By – Cary Denson (BugsFixing Admin)