等待 javascript 回调函数完成

Question

我正在使用 google 存储 api 在异步函数中将文件保存在 gcp 存储桶中。我想等到回调中出现错误或成功，然后我才想继续其他代码行，但我在成功或错误之前收到 LastMessage。

https://googleapis.dev/nodejs/storage/latest/File.html#save

await file.save(jsonData.trim(), {resumable : false}, function(error) {
 if (error) {
   console.log('error');
 } else {
   console.log('success');
 }
})

console.log( "LastMessage: Error or Success is received, only then log this message")

Answer 1

您的 .save() 没有返回承诺。而是给予回调。您可以创建一个传统的承诺方法来获得您想要实现的目标。这是它的代码片段 -


const saveFile = (jsonData) => {
    return new Promise((resolve, reject) => {
        file.save(jsonData.trim(), { resumable: false }, function (error) {
            if (error) {
                console.log('error');
                reject()
            } else {
                console.log('sucess');
                resolve()
            }
        })
    })
}

await saveFile()

console.log("LastMessage: Error or Success is received, only then log this message")

Answer 2

文档中有例子

https://googleapis.dev/nodejs/storage/latest/File.html#save-examples

const {Storage} = require('@google-cloud/storage');
const storage = new Storage();
const myBucket = storage.bucket('my-bucket');

const file = myBucket.file('my-file');
const contents = 'This is the contents of the file.';

file.save(contents, function(err) {
  if (!err) {
    // File written successfully.
  }
});

//-
// If the callback is omitted, we'll return a Promise.
//-
file.save(contents).then(function() {});

您不需要使用 await，对于您的示例，您可以试试这个：

file.save(jsonData.trim(), {resumable : false})
.then(() => nextFunc())
.catch(() => nextFunc())

function nextFunc() {
   console.log( "LastMessage: Error or Success is received, only then log this message")
}

等待 javascript 回调函数完成

Wait for javascript callback function to finish

javascript

google-api

node.js

async-await