I got this array,
var rockets = [
{ country:'Russia', launches:32 },
{ country:'US', launches:23 },
{ country:'China', launches:16 },
{ country:'Europe(ESA)', launches:7 },
{ country:'India', launches:4 },
{ country:'Japan', launches:3 }
];
What do I need to do to return an array mapped, that adds 10 to each
launches
value, here my first approach,
var launchOptimistic = rockets.map(function(elem){
// return elem.launches+10;
return (elem.country, elem.launches+10);
});
console.log(launchOptimistic);
Use .map without return in simple way. Also start using let and const instead of var because let and const is more recommended
const rockets = [
{ country:'Russia', launches:32 },
{ country:'US', launches:23 },
{ country:'China', launches:16 },
{ country:'Europe(ESA)', launches:7 },
{ country:'India', launches:4 },
{ country:'Japan', launches:3 }
];
const launchOptimistic = rockets.map(elem => (
{
country: elem.country,
launches: elem.launches+10
}
));
console.log(launchOptimistic);You're very close already, you just need to return the new object that you want. In this case, the same one except with the launches value incremented by 10:
var rockets = [
{ country:'Russia', launches:32 },
{ country:'US', launches:23 },
{ country:'China', launches:16 },
{ country:'Europe(ESA)', launches:7 },
{ country:'India', launches:4 },
{ country:'Japan', launches:3 }
];
var launchOptimistic = rockets.map(function(elem) {
return {
country: elem.country,
launches: elem.launches+10,
}
});
console.log(launchOptimistic);If you want to alter the original objects, then a simple Array#forEach will do:
rockets.forEach(function(rocket) {
rocket.launches += 10;
});
If you want to keep the original objects unaltered, then use Array#map and copy the objects using Object#assign:
var newRockets = rockets.map(function(rocket) {
var newRocket = Object.assign({}, rocket);
newRocket.launches += 10;
return newRocket;
});