writestream 完成后如何返回承诺? [英] How to return a promise when writestream finishes?

问题描述

我有这样一个函数，它创建一个写流，然后将字符串数组写入文件.我想让它在写作完成后返回一个 Promise.但我不知道如何才能做到这一点.

I have such a function, which create a write stream and then write the string array into the file. I want to make it return a Promise once the writing is finished. But I don't know how I can make this work.

function writeToFile(filePath: string, arr: string[]): Promise<boolean> {
   const file = fs.createWriteStream(filePath);
   arr.forEach(function(row) {
     file.write(row + "
");
   });
   file.end();
   file.on("finish", ()=>{ /*do something to return a promise but I don't know how*/});
}

感谢您的任何评论！

推荐答案

您需要使用 Promise 构造函数:

You'll want to use the Promise constructor:

function writeToFile(filePath: string, arr: string[]): Promise<boolean> {
  return new Promise((resolve, reject) => {
    const file = fs.createWriteStream(filePath);
    for (const row of arr) {
      file.write(row + "
");
    }
    file.end();
    file.on("finish", () => { resolve(true); }); // not sure why you want to pass a boolean
    file.on("error", reject); // don't forget this!
  });
}

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