Exceljs等待在异步功能方面不尽如人意

Question

我目前正在使用exceljs打开和编写excel文件。然而，等待正在犯一个错误。

SyntaxError: await is only valid in async functions and the top level bodies of modules

尽管函数处于异步状态。我如何解决这个问题？下面是我正在使用的代码

async function Process(filename){
  const workbook = new ExcelJS.Workbook();

  let myPromise = new Promise(function(myResolve, myReject) {
    // "Producing Code" (May take some time)
    try{
      await workbook.xlsx.readFile(filename)
      myResolve(); // when successful
    }catch(err){
      myReject();  // when error
    }

  });

  // "Consuming Code" (Must wait for a fulfilled Promise)
  myPromise.then(
    function() {
        /* code if successful */ 
    },
    function() {return false;}
  );
}

Answer 1

同意这些评论，你应该避免Promise constructor antipattern和never use await in the executor of a new Promise！

你应该写

function Process(filename){
  const workbook = new ExcelJS.Workbook();
  
  // "Producing Code" (May take some time)
  let myPromise =  workbook.xlsx.readFile(filename);

  // "Consuming Code"
  return myPromise.then(function() {
    /* code if successful, waiting for a fulfilled Promise */
    return …;
  }, function() {
    /* code when error, waiting for a rejected Promise */
    return false;
  });
}

或

async function Process(filename){
  const workbook = new ExcelJS.Workbook();

  try {
    // "Producing Code" (May take some time)
    await workbook.xlsx.readFile(filename);

    // "Consuming Code" (wait for the promise to be fulfilled)
    return …;
  } catch(err) {
    // Code when error in producing or consuming code
    return false;
  }
}