writestream 完成时如何 return 承诺？

Question

我有这样一个函数，它创建一个写入流，然后将字符串数组写入文件。我想在写作完成后将其设为 return 一个 Promise。但我不知道如何才能使它起作用。

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

感谢您的评论！

Answer 1

您需要 return Promise 才能完成操作。
类似于：

function writeToFile(filePath: string, arr: string[]): Promise<boolean> {
    return new Promise((resolve, reject) => {
        const file = fs.createWriteStream(filePath);
        arr.forEach(function(row) {
            file.write(row + "\n");
        });
        file.end();
        file.on("finish", () => { resolve(true) });
    });
}

Answer 2

您需要使用 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 + "\n");
    }
    file.end();
    file.on("finish", () => { resolve(true); }); // not sure why you want to pass a boolean
    file.on("error", reject); // don't forget this!
  });
}

writestream 完成时如何 return 承诺？

How to return a promise when writestream finishes?

javascript

fs

node.js

promise

typescript