Question

我有这个功能：

const upload = (example) => {
    console.log('uploading...');
    return new Promise(function (resolve, reject) {
        resolve & reject
    });
};

我在这里调用上面的函数：

const dirents = await fs.readdirSync(path, {withFileTypes:true});
await Promise.all(dirents.map(async (dirent) => {
    await upload(example).then((response) => {
        console.log('success');
    }, (err) => {
        console.log(err);
    });
});

输出应为

'uploading' -> 'success' -> 'uploading' ...

但这实际上是

'uploading' -> 'uploading' -> 'success' -> 'success'

我也尝试过（for ... of），但这对我也不起作用。

Answer 1

对于顺序承诺，在public class MainActivity extends AppCompatActivity { protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); final Button button = findViewById(R.id.btn); final Button button1 = findViewById(R.id.button2); final Button button3 = findViewById(R.id.button3); final TextView textView = findViewById(R.id.tex); final EditText et1 = findViewById(R.id.et1); final EditText et2 = findViewById(R.id.et2); final Button button4 = findViewById(R.id.button4); button4.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View arg0) { et1.setText("0"); et2.setText("0"); } }); button1.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View arg0) { textView.setVisibility(View.VISIBLE); Toast.makeText(getApplicationContext(), "done", Toast.LENGTH_SHORT).show(); } }); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View arg0) { Toast.makeText(getApplicationContext(), "done", Toast.LENGTH_SHORT).show(); } }); button3.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View arg0) { String value = et1.getText().toString(); int n11 = Integer.parseInt(value); String value2 = et2.getText().toString(); int n22 = Integer.parseInt(value2); textView.setText(String.valueOf(n22 + n11)); Toast.makeText(getApplicationContext(), "done ", Toast.LENGTH_SHORT).show(); } }); } }函数中使用一个简单的循环非常清晰易读：

async

Answer 2

这是一个将reduce与async/ await（可以运行here）一起使用的现代示例

let userIDs = [1,2,3];

userIDs.reduce( async (previousPromise, nextID) => {
  await previousPromise;
  return upload(nextID).then((val) => {
    console.log("success", val);
  })
}, Promise.resolve());


const upload = (id) => {
    console.log('uploading...', id);
    return new Promise(function (resolve, reject) {
        resolve(id);
    });
};

Answer 3

**您还可以使用递归功能**

select checkin_date, count(pt_Id) as [Number of Patients Seen], 100*sum([esi 1 or 2])/count(pt_Id) as pct
from [Fast Track Quality Research v1]
group by checkin_date

等待诺言循环

3 个答案: