如何在内部 promise 解析后让我的外部 function 返回？

Question

I'm using the Google Sheets API to get some data, and I'm having trouble with the syntax for getting the outer function to return only after the inner function's promise has resolved.

I need getData() to return only after the promise has resolved

async function getData(auth) {
    console.log("GET DATA RAN");
    let sheet = sheetIDGlobal;
    let selectedRow = sheetsRow;
    const sheets = await google.sheets({ version: 'v4', auth });
    console.log("Waiting for Google Sheets reply .....");

    const rowGetter = await sheets.spreadsheets.values.get({
        spreadsheetId: sheet,
        range: selectedRow,
    }, (err, res) => {
        if (err) return console.log('The API returned an error: ' + err);
        const rows = res.data.values;
        if (rows.length) {
            // console.log(rows, "<----- ROWS");
            promises = rows.forEach((row) => {
                section = `${row[0]}`
                // just saving some variables here
            })
            function runIfFirst() {
                if (tracker === 0) {
                    fillDataPropType(auth)
                }
            }
            Promise.resolve(promises).then(runIfFirst());
        } else {
            console.log('No data found.');
        }
    })
    // trying to get the outer function to return after the inner function is complete.
    return await rowGetter;
}

I tried assigning the inner function to a variable and awaiting the reply for that variable to be returned but I don't understand what I need to do to have the outer function wait on the inner function.

Answer 1

It seems that the issue is that in this part, you are mixing a callback and a promise.

const rowGetter = await sheets.spreadsheets.values.get({
  spreadsheetId: sheet,
  range: selectedRow,
}, (err, res) => { /* ... */ })

I suppose the spreadsheets API supports both. Using await here means you expect it returns a promise, so you shouldn't pass a callback function to the second argument. If you want to use a callback, then no await is required. It won't return anything either. You only need to choose one.

I think promise + await is probably easier to understand:

const res = await sheets.spreadsheets.values.get({
  spreadsheetId: sheet,
  range: selectedRow,
})
const rows = res.data.values;
if (rows.length) {
  // omitted...
}
// omitted...
return rowGetter;

I'm not sure what is the rowGetter , but you just need to remove the callback argument and move those code outside.

Or, if you decided to use the callback, but still want the getData() to return a promise, then you need to convert it to a promise yourself. For example:

return new Promise((resolve, reject) => {
  sheets.spreadsheets.values.get({
    spreadsheetId: sheet,
    range: selectedRow,
  }, (err, res) => {
    if (err) {
      reject(err);
      return console.log('The API returned an error: ' + err);
    }
    const rows = res.data.values;
    // omitted ...
    resolve(rowGetter);
  });  
});

In this case, you don't await sheets.spreadsheets.values.get and it won't return anything. Because the return value is the res in the callback function.