JS地图返回对象

Question

我有这个阵列,

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 }
];

我需要做什么来返回一个映射的数组,每个数组都加10

发布会

价值,这是我的第一个方法,

var launchOptimistic = rockets.map(function(elem){
  // return  elem.launches+10;
     return (elem.country, elem.launches+10);


});
console.log(launchOptimistic);

Answer 1

你已经非常接近了,你只需要返回你想要的新对象.在这种情况下,相同的一个除了启动值增加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);

Answer 2

以简单的方式使用.map而不返回.也开始使用let和const而不是var,因为更推荐let和const

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);

Answer 3

最干净的解决方案是解构。

const rockets = [
        { country:'Russia', launches:32 },
        { country:'US', launches:23 },
        { country:'China', launches:16 },
        { country:'Europe(ESA)', launches:7 },
        { country:'India', launche`enter code here`s:4 },
        { country:'Japan', launches:3 }
    ];
    const updated = rockets.map(rocket=>{
    return {...rocket,launches:rocket.launches+10}
    });

Answer 4

如果你想改变原始对象，那么一个简单的方法Array#forEach就可以了：

rockets.forEach(function(rocket) {
    rocket.launches += 10;
});

如果要保持原始对象不变，请使用Array#map并使用Object#assign以下方法复制对象：

var newRockets = rockets.map(function(rocket) {
    var newRocket = Object.assign({}, rocket);
    newRocket.launches += 10;
    return newRocket;
});

Answer 5

map 火箭并为其发射增加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 }
];
rockets.map((itm) => {
    itm.launches += 10
    return itm
})
console.log(rockets)

如果您不想修改rockets，可以执行以下操作：

var plusTen = []
rockets.forEach((itm) => {
    plusTen.push({'country': itm.country, 'launches': itm.launches + 10})
})