javascript - 异步/等待上传任务

Question

如何等待 uploadTask 以便我可以先上传图像/文件并跟踪其进度，然后再将下载 url dan 文档插入到 Firestore，

以下代码是我的示例 Vue 项目。它可以正常工作，但请参阅 if (portraitFile) ，必须在必须上传图片的条件下，不想上传图片怎么办？

它必须移出那个条件 if ，但它会在文件完成并检索到下载 URL 之前异步执行。

目标:将 firestore add() 移到uploadTask 的完成回调/参数之外。

    async commitCharacter() {
      try {
        let character = this.character;
        let portraitFile = this.portraitFile;

        if (portraitFile) {
          const uploadTask = storageRef
            .child(`characters/${character.id}/portrait.png`)
            .put(portraitFile, { contentType: "image/png" });

          await uploadTask.on(
            "state_changed",
            snapshot => {
              this.portraitUploadProgress =
                (snapshot.bytesTransferred / snapshot.totalBytes) * 100;
            },
            null,
            async () => {
              character.portraitUrl = await storageRef
                .child(`characters/${character.id}/portrait.png`)
                .getDownloadURL();

              if (character.id) {
              await db
                .collection("characters")
                .doc(character.id)
                .update(character);
              } else {
                character.id = (await 
                db.collection("characters").add(character)).id;
              }

              $("#manageCharacter").modal("hide");
            }
          );
        }
      }

Answer 1

你可以把你的 uploadTask在 promise 中:

async function uploadTaskPromise() {
  return new Promise(function(resolve, reject) {
    const storageRef = storage.ref(YOUR_STORAGE_PATH)
    const uploadTask = storageRef.put(YOUR_FILE_OR_BLOB)
    uploadTask.on('state_changed',
      function(snapshot) {
        var progress = (snapshot.bytesTransferred / snapshot.totalBytes) * 100
        console.log('Upload is ' + progress + '% done')
      },
      function error(err) {
        console.log('error', err)
        reject()
      },
      function complete() {
        uploadTask.snapshot.ref.getDownloadURL().then(function(downloadURL) {
          resolve(downloadURL)
        })
      }
    )
  })
}

然后像这样使用它:

const storageUrl = await uploadTaskPromise()
console.log(storageUrl) // do whatever you want with the URL...