尝试下载多个文件时如何检查Firebase存储中是否存在文件 - javascript

Question

我有一个需要从 Firebase 存储下载的文件夹和文件名称的 Arrylist。

它抛出异常是因为某些文件夹和文件在 firebase storage 中不存在。 是否可以在不引发异常的情况下检测文件夹和文件？

JS 代码：

var parNum = 'S3DD4';
var sessionNum = '3333';
var storageInfoarr = ["Testing/Testing1.3gp", "Testing/Testing1.xlsx"];
 for (i = 0 ; i< storageInfoarr.length; i++){
    var starsRef = storageRef.child(parNum+'/'+sessionNum+'/'+storageInfoarr[i])
    var urlString = starsRef.getDownloadURL().catch(function(error) {
    switch (error.code) {
      case 'storage/object_not_found': // <<< here you decide what to do when the file doesn't exist
        // File doesn't exist
        break;

      case 'storage/unauthorized':
        // User doesn't have permission to access the object
        break;

      case 'storage/canceled':
        // User canceled the upload
        break;

    }
  });

Answer 1

getDownloadUrl() 总是会在路径不正确时抛出异常，你可以做的是处理这些异常并且只下载存在的文件。您可以创建一个合并的 Promise 来判断某些路径是否正确和不正确，并相应地处理它们。

var parNum = 'S3DD4';
var sessionNum = '3333';
var storageInfoarr = ["Testing/Testing1.3gp", "Testing/Testing1.xlsx"];

Promise.all(storageInfoarr.map((sStorage) => {
    var starsRef = storageRef.child(parNum+'/'+sessionNum+'/'+sStorage);
    starsRef.getDownloadURL().then(url => {
        // url is download url, use it download the file
    }).catch(err => {
       // Here you can handle the error for individual download
    });
}) ).then((aResponses) => {
   // This will be called if all promises are resolved. aResponses contain all download url
}).catch((err) => {
   // This will be called if any of the download path is incorrect, with the error of first promise which fails
});