节点js-将数据写入可写流

Question

In my node application im writing data to the file using write method in the createWriteStream method.Now i need to find whether the write for the particular stream is complete or not.How can i find that.

var stream = fs.createWriteStream('myFile.txt', {flags: 'a'});
var result = stream.write(data);

writeToStream();
function writeToStream() {
  var result = stream.write(data + '\n');
  if (!result) {
    stream.once('drain',writeToStream());
  }
}

I need to call other method for every time when write completes.How can i do this.

Answer 1

From the node.js WritableStream.write(...) documentation you can give the "write" method a callback that is called when the written data is flushed:

var stream = fs.createWriteStream('myFile.txt', {flags: 'a'});
var data = "Hello, World!\n";
stream.write(data, function() {
  // Now the data has been written.
});

Note that you probably don't need to actually wait for each call to "write" to complete before queueing the next call. Even if the "write" method returns false you can still call subsequent writes and node will buffer the pending write requests into memory.

Answer 2

I am using maerics's answer along with error handling. The flag 'a' is used to Open file for appending. The file is created if it does not exist. There Other flags you can use.

// Create a writable stream &  Write the data to stream with encoding to be utf8
    var writerStream = fs.createWriteStream('MockData/output.txt',{flags: 'a'})
                         .on('finish', function() {
                              console.log("Write Finish.");
                          })
                         .on('error', function(err){
                             console.log(err.stack);
                          });


    writerStream.write(outPutData,function() {
      // Now the data has been written.
        console.log("Write completed.");
    });

    // Mark the end of file
    writerStream.end();