new stream.Writable([options])

• options <Object>
  • highWaterMark <number> stream.write() 开始返回 false 时的缓冲级别。 默认值: 16384 (16KB) 或 16 表示 objectMode 流。
  • decodeStrings <boolean> 是否将传给 stream.write() 的 string 编码为 Buffer（使用 stream.write() 调用中指定的编码），然后再将它们传给 stream._write()。 其他类型的数据不会被转换（即 Buffer 不会被解码为 string）。 设置为 false 将阻止 string 被转换。 默认值: true。
  • defaultEncoding <string> 当没有将编码指定为 stream.write() 的参数时使用的默认编码。 默认值: 'utf8'。
  • objectMode <boolean> stream.write(anyObj) 是否为有效操作。 当设置后，如果流实现支持，则可以写入字符串、Buffer 或 Uint8Array 以外的 JavaScript 值。 默认值: false。
  • emitClose <boolean> 流被销毁后是否应该触发 'close'。 默认值: true。
  • write <Function> stream._write() 方法的实现。
  • writev <Function> stream._writev() 方法的实现。
  • destroy <Function> stream._destroy() 方法的实现。
  • final <Function> stream._final() 方法的实现。
  • autoDestroy <boolean> 此流是否应在结束后自动调用自身的 .destroy()。 默认值: false。

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

class MyWritable extends Writable {
  constructor(options) {
    // 调用 stream.Writable() 构造函数。
    super(options);
    // ...
  }
}

或者，当使用 ES6 之前的风格构造函数时：

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

function MyWritable(options) {
  if (!(this instanceof MyWritable))
    return new MyWritable(options);
  Writable.call(this, options);
}
util.inherits(MyWritable, Writable);

或者，使用简化的构造函数方法：

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

const myWritable = new Writable({
  write(chunk, encoding, callback) {
    // ...
  },
  writev(chunks, callback) {
    // ...
  }
});

• options <Object>
  • highWaterMark <number> Buffer level when stream.write() starts returning false. Default: 16384 (16KB), or 16 for objectMode streams.
  • decodeStrings <boolean> Whether to encode strings passed to stream.write() to Buffers (with the encoding specified in the stream.write() call) before passing them to stream._write(). Other types of data are not converted (i.e. Buffers are not decoded into strings). Setting to false will prevent strings from being converted. Default: true.
  • defaultEncoding <string> The default encoding that is used when no encoding is specified as an argument to stream.write(). Default: 'utf8'.
  • objectMode <boolean> Whether or not the stream.write(anyObj) is a valid operation. When set, it becomes possible to write JavaScript values other than string, Buffer or Uint8Array if supported by the stream implementation. Default: false.
  • emitClose <boolean> Whether or not the stream should emit 'close' after it has been destroyed. Default: true.
  • write <Function> Implementation for the stream._write() method.
  • writev <Function> Implementation for the stream._writev() method.
  • destroy <Function> Implementation for the stream._destroy() method.
  • final <Function> Implementation for the stream._final() method.
  • autoDestroy <boolean> Whether this stream should automatically call .destroy() on itself after ending. Default: false.

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

class MyWritable extends Writable {
  constructor(options) {
    // Calls the stream.Writable() constructor.
    super(options);
    // ...
  }
}

Or, when using pre-ES6 style constructors:

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

function MyWritable(options) {
  if (!(this instanceof MyWritable))
    return new MyWritable(options);
  Writable.call(this, options);
}
util.inherits(MyWritable, Writable);

Or, using the simplified constructor approach:

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

const myWritable = new Writable({
  write(chunk, encoding, callback) {
    // ...
  },
  writev(chunks, callback) {
    // ...
  }
});