如果语句匹配，如何重置 forEach() function [NodeJS]

Question

const downloadurl = ['url1', 'url2']
const filename = 'run.jar'

downloadurl.forEach((urls) => {
    https.get(urls, (httpsres) => {
        const path = `${installationdirectory}/${filename}`
        const filePath = fs.createWriteStream(path);
        httpsres.pipe(filePath);
        filePath.on('finish',() => {

            filePath.close();
            const filesize = fs.statSync(path).size
            // Verify if the size of the file is smaller than 1Kb
            if((filesize / 1024) < 1) return;

            // Want to skip this console.log if the file size is smaller than 1Kb and try with the other downloadurl (Hence why the downloadurl.forEach)
            console.log('File downloaded!'); 


        })
    })
})

基本上，我使用的是来自 NodeJS 的 https 模块，如果下载 url 不存在，它不会给出错误，因为它只是创建一个 1 字节文件，而不是名称为run.jar 。 所以，如果文件的大小小于1Kb，我想让它停止执行代码并尝试与其他URL一起下载，有什么想法吗？

Answer 1

1. 你可以使用every() 循环。 当你想打破循环时，不要返回任何东西。

// Prints "1, 2, 3"
[1, 2, 3, 4, 5].every(v => {
  if (v > 3) {
    return false;
  }

  console.log(v);
  // Make sure you return true. If you don't return a value, `every()` will stop.
  return true;
});

2. 或者您可以使用第三个更改数组的长度

const myNums = [1, 2, 3, 4, 5];
myNums.forEach((v, index, arr) => {
  console.log(v);
  if (val > 3) {
    arr.length = index + 1; // Behaves like `break`
  }
}

Answer 2

如果您现在使用回调结构，您可以尝试递归 function 以尝试进一步下载。

function tryDownload(downloadUrls):
    // try download the first
    https.get(downloadUrls[0], (res) => {
        // read it, etc
        // ...

        // if too small, try the next urls
        if ((filesize / 1024) < 1)
            tryDownload(downloadUrls.slice(1));
        else
            // success!
            // ...
    })

不过，您可能会发现将其重组为异步 function 很清楚。 在伪代码中：

    for each url in download urls
        res = await download url
        if res indicates success
            handle the res
            return

Answer 3

使用@Matt 的答案，因为它是最简单的实现（而且我不知道 HTTPS 模块确实有检查状态码的响应）。 谢谢所有回答的人^^

    const downloadurl = ['url1', 'url2']
    const filename = 'run.jar'
    
    downloadurl.forEach((urls) => {
        https.get(urls, (httpsres) => {
            if(httpsres.statusCode !== 200) {
                return console.log(`Attempt of downloading failed with ${httpsres.statusCode} error! Retrying with another download URL`);
            } else {
    
            const path = `${installationdirectory}/${filename}`
            const filePath = fs.createWriteStream(path);
            httpsres.pipe(filePath);
            filePath.on('finish',() => {
    
                filePath.close();
                const filesize = fs.statSync(path).size
                // Verify if the size of the file is smaller than 1Kb
                if((filesize / 1024) < 1) return;
    
                // Want to skip this console.log if the file size is smaller than 1Kb and try with the other downloadurl (Hence why the downloadurl.forEach)
                console.log('File downloaded!'); 
    
            })
            }
        })
    })
    ```