javascript - Node.JS through2 回调

Question

我是 Node.JS 的新手，正在尝试理解 through2图书馆。

我想知道回调(在从上面链接复制的以下示例代码中)是如何有用的。如果可能，请使用一小段代码进行解释。

fs.createReadStream('ex.txt')
  .pipe(through2(function (chunk, enc, callback) {
    for (var i = 0; i < chunk.length; i++)
      if (chunk[i] == 97)
        chunk[i] = 122 // swap 'a' for 'z' 

    this.push(chunk)

    callback()
   }))
  .pipe(fs.createWriteStream('out.txt'))

Answer 1

我认为需要继续管道链接。如果你不调用它，管道就会破裂。

此声明来自through2 documentation :

A minimal implementation should call the callback function to indicate that the transformation is done, even if that transformation means discarding the chunk.