I am reading a .txt file data and calling the 3rd party api to fetch more data using .txt file data as arguments continuously. For that I am running an await Promise.all() with map() loop using setTimeOut() function of delay 2 seconds so that 3rd party API gets latency time and avoid catch error.

After that I am appending/pushing it to a json object array. After that Writing the whole JSON.stringify(data) to a .json file. I want everything in a sequence. But unfortunately while debugging, what I see is that the writeFileSync gets executed even before loop completion which I dont want.

Here is my code I am trying:

const writeFile = async (obj) => {
  const json = JSON.stringify(obj);
  fs.writeFileSync('/home/deb/Downloads/Twitty-Bird/src/utils/output.json', json, 'utf8')
  return 'completed';
}

export const convertToJSONFile = async () => {
  try {
    let obj = {
      table: []
    };
    const data = fs.readFileSync('/home/deb/Downloads/Twitty-Bird/src/utils/sample.txt', 'utf8');
    if (!data) throw err;
    let splitted = data.toString().split("\n");
    let interval = 2000;
    await Promise.all(splitted.map(async (word, index) => {
      setTimeout(async function () {
        let wordMeaningDetails = await axios({
        method: 'GET',
        url: `https://api.dictionaryapi.dev/api/v2/entries/en/${word}`
        })
        wordMeaningDetails = wordMeaningDetails.data[0].meanings[0].definitions[0]
        obj.table.push({
          word: word, definition: wordMeaningDetails.definition, example: wordMeaningDetails.example
        });
      }, interval);
    }))

    const res = await writeFile(obj);
    console.log(res);
  }
  catch (err) {
    console.log("Error = ", err);
    //convertToJSONFile();
  }
}

convertToJSONFile();

What I want exactly in order in laymein terms:

1. First read all data and split into array using fs.readFileSync
2. Execute 3rd party api with axios one by one and append all data to object obj = {}
3. Then finally write that json data to a .json file and save it in root folder.

CodePudding user response：

You need to return a Promise in the map function. See below:

await Promise.all(splitted.map(async (word, index) => ...)));
// You need to return a promise not a anonymous function because the function
// will resolve instantely and is not waiting for your timeout

(async () => {

  await Promise.all([1, 2, 3].map((word, index) => new Promise((resolve) => {
    setTimeout(async function() {
      console.log(word);
      // do your api stuff
      resolve(); // resolve the promise to mark it as "done"
    }, 1000 * index)
  })))
  console.log("done!")

})();