如何从诺言中添加元素组件

Question

我正在尝试将其源设置为下载URL来创建映像，该映像由.getDownloadURL（）函数从firebase中检索到。我还想将图像的ID设置为Firebase存储路径，以便获取图像的名称。但是问题是，当我尝试在.getDownloadURL（）函数中创建路径时，它说“无法获取未定义的位置”，因为path变量的作用域没有到达内部。我尝试的解决方案是在进入.getDownloadUrl（）函数之前创建图像并添加ID，但是由于img是未定义的，所以我无法设置img的.src。无论如何，我将不胜感激，感谢您的宝贵时间。这是我的代码：

for(n=0; n<subarray.length; n++){
                        //add image with url src
                        var path = subarray[n].location.path_; //I want the img ID to be this
                        var img = document.createElement("IMG"); //this is the IMG
                        img.id = path;
                        storage.ref(subarray[n].location.path_).getDownloadURL().then(function(url, img){
                            img.src = url; //error says cannot set .src of undefined
                            column = "column" + columnNr //columnNr is defined earlier as 1
                            columnNr = columnNr + 1;
                            if(columnNr > 4){
                                columnNr = 1;
                            }
                            document.getElementById(column).appendChild(img);
                        });
                    }

Answer 1

由于您在img方法中添加了无效的undefined参数，因此您正在用img覆盖变量then()

只需将其删除，如下所示：

for(n=0; n<subarray.length; n++){
                        //add image with url src
                        var path = subarray[n].location.path_; //I want the img ID to be this
                        var img = document.createElement("IMG"); //this is the IMG
                        img.id = path;
                        storage.ref(subarray[n].location.path_).getDownloadURL().then(function(url){
                            img.src = url; //error says cannot set .src of undefined
                            column = "column" + columnNr //columnNr is defined earlier as 1
                            columnNr = columnNr + 1;
                            if(columnNr > 4){
                                columnNr = 1;
                            }
                            document.getElementById(column).appendChild(img);
                        });
                    }