如何将nodejs计数器可读的流示例转换为简化的施工版本？

Question

我参考此doc

_construct（）方法在我的版本中从未调用。为什么？

注意：在简化的构造中，您提供了 _CONSTRUCT（）方法的实现。 }

这是一个可读的流计数器的工人阶级版本：

const { Readable } = require('stream');

class Counter extends Readable {
  constructor(options) {
    super(options);
    this._max = 10;
    this._index = 1;
  }

  _read() {
    const i = this._index++;
    if (i > this._max) {
      this.push(null);
    } else {
      const str = String(i);
      const buf = Buffer.from(str, 'utf-8');
      this.push(buf);
    }
  }
}

const readable = new Counter();

readable.on('readable', function() {
  console.log('readable');

  let data;

  while ((data = this.read()) !== null) {
    console.log(String(data));
  }
});

readable.on('close', function() {
  console.log('close');
});

这是我无法使用的简化施工版本：

const { Readable } = require('stream');

const counter = new Readable({

  construct() {
    this._max = 10;
    this._index = 1;
    console.log(this._max); // This is never executed
  },

  read() {
    console.log(this._max); // This is undefined
    this.push(null);
  }

  // read() {
  //   const i = this._index++;
  //   if (i > this._max) {
  //     this.push(null);
  //   } else {
  //     const str = String(i);
  //     const buf = Buffer.from(str, 'utf-8');
  //     this.push(buf);
  //   }
  // }

});

counter.on('readable', function() {
  let data;

  while ((data = this.read()) !== null) {
    console.log(String(data));
  }
});

counter.on('close', function() {
  console.log('close');
});

文档说：

const { Writable } = require('node:stream');

const myWritable = new Writable({
  construct(callback) {
    // Initialize state and load resources...
  },
  write(chunk, encoding, callback) {
    // ...
  },
  destroy() {
    // Free resources...
  }
});

现在我很困惑。认为初始化代码属于 _CONSTRUCT（）方法？

Answer 1

如我上面的评论所述， _CONSTRUCT（）在节点版本15.x中添加。为了进一步参考，请按照以下示例：

const { Readable } = require('stream');

const counter = new Readable({

  construct(callback) {
    this._max = 10;
    this._index = 1;
    callback(); // Signal completion of initialization
  },

  read() {
    const i = this._index++;
    if (i > this._max) {
      this.push(null);
    } else {
      const str = String(i);
      const buf = Buffer.from(str, 'utf-8');
      this.push(buf);
    }
  }

});

counter.on('readable', function() {
  let data;

  while ((data = this.read()) !== null) {
    console.log(String(data));
  }
});

counter.on('close', function() {
  console.log('close');
});