可写流的示例

下面说明了一个相当简单（有些毫无意义）的自定义 Writable 流的实现。 虽然这个特定的 Writable 流实例没有任何真正的特殊用途，但该示例说明了自定义 Writable 流实例的每个必需元素：

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

class MyWritable extends Writable {
  _write(chunk, encoding, callback) {
    if (chunk.toString().indexOf('a') >= 0) {
      callback(new Error('chunk is invalid'));
    } else {
      callback();
    }
  }
}

The following illustrates a rather simplistic (and somewhat pointless) custom Writable stream implementation. While this specific Writable stream instance is not of any real particular usefulness, the example illustrates each of the required elements of a custom Writable stream instance:

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

class MyWritable extends Writable {
  _write(chunk, encoding, callback) {
    if (chunk.toString().indexOf('a') >= 0) {
      callback(new Error('chunk is invalid'));
    } else {
      callback();
    }
  }
}