Node.js 使用转换流将JS对象转换为JSON

请注意，有许多变换流可以执行此操作：

JSON->JS

但我希望创建一个Node.js转换流，它可以：

JS->JSON

我有一个可读的流：

const readable = getReadableStream({objectMode:true});

可读流输出对象，而不是字符串

我需要创建一个转换流，它可以过滤其中一些对象，并将这些对象转换为JSON，如下所示：

const t = new Transform({
  objectMode: true,
  transform(chunk, encoding, cb) {
    if(chunk && chunk.marker === true){
       this.push(JSON.stringify(chunk));
     }
    cb();
  },
  flush(cb) {
    cb();
  }
});

但是，由于某些原因，我的转换流无法接受转换方法的对象，只有字符串和缓冲区，我能做什么？

我尝试添加这两个选项：

  const t = new Transform({
      objectMode: true,
      readableObjectMode: true,  // added this
      writableObjectMode: true,  // added this too
      transform(chunk, encoding, cb) {
        this.push(chunk);
        cb();
      },
      flush(cb) {
        cb();
      }
    });

---

不幸的是，我的转换流仍然不能接受对象，只能接受字符串/缓冲区。

您只需要在转换流上使用

writeableobjectmode:true

options <Object> Passed to both Writable and Readable constructors. Also has the following fields:
    readableObjectMode <boolean> Defaults to false. Sets objectMode for readable side of the stream. Has no effect if objectMode is true.
    writableObjectMode <boolean> Defaults to false. Sets objectMode for writable side of the stream. Has no effect if objectMode is true.

const { Readable, Writable, Transform } = require('stream');

let counter = 0;

const input = new Readable({
  objectMode: true,
  read(size) {
    setInterval( () => {
      this.push({c: counter++});  
    }, 1000);  
  }  
});

const output = new Writable({
  write(chunk, encoding, callback) {
    console.log('writing chunk: ', chunk.toString());
    callback();  
  }  
});

const transform = new Transform({
  writableObjectMode: true,
  transform(chunk, encoding, callback) {
    this.push(JSON.stringify(chunk));
    callback();  
  }  
});

input.pipe(transform);
transform.pipe(output);