javascript - 如何从 Google Places 获取一系列地点的坐标，然后在完成所有操作后使用结果？

Question

我有一组地名，例如:

const places = ['King Square, London', 'Empire State Building', 'Great Wall of China'];

我需要一个新的对象数组，其中为地名数组中的每个元素设置了位置，例如:

const places = [
  { name: 'King Square, London', position: { latitude: ..., longitude: ... } },
  ...
];

我认为我必须做这样的事情:

const places = [];

['King Square, London', 'Empire State Building', 'Great Wall of China'].forEach(placeName => {
  axios
  .get(`https://maps.googleapis.com/maps/api/place/textsearch/json?key=GOOGLE_PLACES_API_KEY&query=${placeName}`)
  .then(response => {
    if (!!response && !!response.results && !!response.results[0]) {
      const searchResult = response.results[0];

      if (!!searchResult) {
        axios
          .get(`https://maps.googleapis.com/maps/api/place/details/json?key=GOOGLE_PLACES_API_KEY&placeid=${searchResult.place_id}`)
          .then(response => {
            const placeResult = response.result;

            if (!!placeResult) {
              places.push({ name: placeName, position: placeResult.geometry.location })

但是好像不行。

它应该是什么样子才能填充 places 并在填充后使用数组？在使用它之前，我是否必须使用 Promises 来确保它已被填充？

Answer 1

使用Promise.all() .

更新现有代码的步骤:

1. 使用 Array.map() 将 promise 存储在数组中而不是 forEach() .
2. 回拨给map() 返回 promise (即来自 axios.get().then() 的返回值)。
3. 对 axios.get() 的调用的响应将有一个包含结果的 data 属性，因此使用 response.data.results 而不是 response.results
4. 再次兑现 promise

5. 然后在设置了 promises 数组之后，就可以使用 Promise.all() 了:

   const places = [];
   //1 - store promises in an array
   var promises = ['King Square, London', 'Empire State Building', 'Great Wall of China'].map(placeName => {
     return axios //2 - return promise
     .get(`https://maps.googleapis.com/maps/api/place/textsearch/json?key=GOOGLE_PLACES_API_KEY&query=${placeName}`)
     .then(response => {
       //3 - use response.data.results instead of response.results
       if (!!response && !!response.data && !!response.data.results && !!response.data.results[0]) {
         const searchResult = response.data.results[0];
   
         if (!!searchResult) {
           return axios //4 return nested promise
             .get(`https://maps.googleapis.com/maps/api/place/details/json?key=GOOGLE_PLACES_API_KEY&placeid=${searchResult.place_id}`)
             .then(response => {
               const placeResult = response.data.result;
   
               if (!!placeResult) {
                 places.push({ name: placeName, position: placeResult.geometry.location });
               }
             })
         }
       }
     });
   });
   //5 - After promises are done, use the places array
   Promise.all(promises).then(results => {
       console.log('places:', places);
   })
   

输出:

places: [ { name: 'King Square, London',
    position: { lat: 51.52757920000001, lng: -0.0980441 } },
  { name: 'Great Wall of China',
    position: { lat: 40.4319077, lng: 116.5703749 } },
  { name: 'Empire State Building',
    position: { lat: 40.7484405, lng: -73.98566439999999 } } ]

客户端 Javascript 示例

下面是(客户端)JavaScript 的端口。请注意它非常相似，但使用了 StackOverflow API(因为那样不会有 CORS 问题)。

var ranks = [];
var promises = [94, 95].map(badgeId => {
  return axios.get(`https://api.stackexchange.com/2.2/badges/${badgeId}?site=stackoverflow&order=desc&sort=rank&filter=default`)
    .then(response => {
      var responsebadgeId = response.data.items[0].badge_id;
      return axios.get(`https://api.stackexchange.com/2.2/badges/${responsebadgeId}/recipients?site=stackoverflow`)
        .then(response => {
          console.log('pushing rank into array from data: ',response.data.items[0].rank);
          ranks.push(response.data.items[0].rank);
        });
    });
});
Promise.all(promises).then(responses => {
  console.log('promises all callback - ranks:',ranks);
});

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