对象模式的双工流

对于 Duplex 流，可以分别使用 readableObjectMode 和 writableObjectMode 选项为 Readable 或 Writable 侧专门设置 objectMode。

例如，在下面的示例中，创建了新的 Transform 流（它是 Duplex 流），它具有对象模式的 Writable 端，该端接受 JavaScript 数字，这些数字在 Readable 端转换为十六进制字符串。

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

// 所有转换流也是双工流。
const myTransform = new Transform({
  writableObjectMode: true,

  transform(chunk, encoding, callback) {
    // 如有必要，将块强制为数字。
    chunk |= 0;

    // 将块转换为其他东西。
    const data = chunk.toString(16);

    // 将数据推送到可读队列中。
    callback(null, '0'.repeat(data.length % 2) + data);
  }
});

myTransform.setEncoding('ascii');
myTransform.on('data', (chunk) => console.log(chunk));

myTransform.write(1);
// 打印: 01
myTransform.write(10);
// 打印: 0a
myTransform.write(100);
// 打印: 64

For Duplex streams, objectMode can be set exclusively for either the Readable or Writable side using the readableObjectMode and writableObjectMode options respectively.

In the following example, for instance, a new Transform stream (which is a type of Duplex stream) is created that has an object mode Writable side that accepts JavaScript numbers that are converted to hexadecimal strings on the Readable side.

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

// All Transform streams are also Duplex Streams.
const myTransform = new Transform({
  writableObjectMode: true,

  transform(chunk, encoding, callback) {
    // Coerce the chunk to a number if necessary.
    chunk |= 0;

    // Transform the chunk into something else.
    const data = chunk.toString(16);

    // Push the data onto the readable queue.
    callback(null, '0'.repeat(data.length % 2) + data);
  }
});

myTransform.setEncoding('ascii');
myTransform.on('data', (chunk) => console.log(chunk));

myTransform.write(1);
// Prints: 01
myTransform.write(10);
// Prints: 0a
myTransform.write(100);
// Prints: 64