类型错误属性 然后是未定义的

Question

Var Map, CachedGeoJson;
var promise = that.map.data.loadGeoJson('https://api.myjson.com/bins/31e3j'); 
promise.then(function(data) {
    cachedGeoJson = data; 
    map.data.addGeoJson(
        'https://api.myjson.com/bins/31e3j',
        { idPropertyName: "id"}
    );

Answer 1

你需要关闭你的函数，像这样修复语法：

Var Map, CachedGeoJson;
var promise = that.map.data.loadGeoJson('https://api.myjson.com/bins/31e3j');
promise.then(function(data) {
    cachedGeoJson = data; 
    map.data.addGeoJson(
        'https://api.myjson.com/bins/31e3j',
        { idPropertyName: "id"}
    );
});

Answer 2

您可以尝试创建一个不同的函数来创建 promise 对象，因为 google loadGeoJson 不会返回 promise 对象。

function loadGeoJson(url, options) {
    var promise = new Promise(function (resolve, reject) {
      try {
        that.map.data.loadGeoJson(url, options, function (features) {
            resolve(features);
        });
      } catch (e) {
        reject(e);
      }
    });
    return promise;
}
var promise = loadGeoJson('studs.json');
promise.then(function (features) {
    map.data.addGeoJson(
        'https://api.myjson.com/bins/31e3j',
        { idPropertyName: "id"}
    );
});

Answer 3

你可以检查承诺中存在哪些属性。

for (var property in promise) {
    if (promise.hasOwnProperty(property)){
        alert(property);
    }
}