Node.js Stream writable.writableEnded 属性

writable.writableEnded 属性是 Stream 模块的内置应用程序编程接口，用于检查 writable.end() 方法是否被调用。

句法：

writable.writableEnded 

返回值：如果在调用 writable.end() 方法之前返回 true，否则返回 false。

下面的例子说明了 Node.js 中writable.writableEnded 属性的使用：

示例 1：

// Node.js program to demonstrate the     
// writable.writableEnded Property
  
// Accessing stream module
const stream = require('stream');
  
// Creating a stream and creating 
// a write function
const writable = new stream.Writable({
  
  // Write function with its 
  // parameters
  write: function(chunk, encoding, next) {
  
    // Converting the chunk of
    // data to string
    console.log(chunk.toString());
    next();
  }
});
  
// Writing data
writable.write('hi');
  
// Again writing some data
writable.write('GFG');
  
// Calling end function
writable.end();
  
// Calling writable.writableEnded
// Property
writable.writableEnded;
  
// Calling destroy function
//to display output
writable.destroy();

输出：

hi
GFG
Writable {
  _writableState:
   WritableState {     objectMode: false,
     highWaterMark: 16384,
     finalCalled: false,
     needDrain: false,
     ending: true,
     ended: true,
     finished: false,
     destroyed: true,
     decodeStrings: true,
     defaultEncoding: 'utf8',
     length: 0,
     writing: false,
     corked: 0,
     sync: false,
     bufferProcessing: false,
     onwrite: [Function: bound onwrite],
     writecb: null,
     writelen: 0,
     bufferedRequest: null,
     lastBufferedRequest: null,
     pendingcb: 2,
     prefinished: true,
     errorEmitted: false,
     emitClose: true,
     autoDestroy: false,
     bufferedRequestCount: 0,
     corkedRequestsFree:
      { next: null,
        entry: null,
        finish: [Function: bound onCorkedFinish] } },
  writable: false,
  _write: [Function: write],
  domain: null,
  _events: [Object: null prototype] {},
  _eventsCount: 0,
  _maxListeners: undefined }

在这里，您可以看到上例中的 end 属性被设置为 true。

示例 2：

// Node.js program to demonstrate the     
// writable.writableEnded Property
  
// Accessing stream module
const stream = require('stream');
  
// Creating a stream and creating 
// a write function
const writable = new stream.Writable({
  
  // Write function with its 
  // parameters
  write: function(chunk, encoding, next) {
  
    // Converting the chunk of
    // data to string
    console.log(chunk.toString());
    next();
  }
});
  
// Writing data
writable.write('hi');
  
// Again writing some data
writable.write('GFG');
  
// Calling writable.writableEnded
// Property
writable.writableEnded;
  
// Calling destroy function
//to display output
writable.destroy();

输出：

hi
GFG
Writable {
  _writableState:   WritableState {
     objectMode: false,
     highWaterMark: 16384,
     finalCalled: false,
     needDrain: false,
     ending: false,
     ended: false,
     finished: false,
     destroyed: true,
     decodeStrings: true,
     defaultEncoding: 'utf8',
     length: 0,
     writing: false,
     corked: 0,
     sync: false,
     bufferProcessing: false,
     onwrite: [Function: bound onwrite],
     writecb: null,
     writelen: 0,
     bufferedRequest: null,
     lastBufferedRequest: null,
     pendingcb: 2,
     prefinished: false,
     errorEmitted: false,
     emitClose: true,
     autoDestroy: false,
     bufferedRequestCount: 0,
     corkedRequestsFree:
      { next: null,
        entry: null,
        finish: [Function: bound onCorkedFinish] } },
  writable: true,
  _write: [Function: write],
  domain: null,
  _events: [Object: null prototype] {},
  _eventsCount: 0,
  _maxListeners: undefined }

在上面的示例中，end 属性设置为 false，因为在调用 writable.writableEnded 属性之前未调用 writable.end() 方法。

参考： https://nodejs.org/api/stream.html#stream_writable_writableended