Node js-将数据写入可写流
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Node js- writing data to the writable stream
提问by sachin
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.
在我的节点应用程序中，我使用 createWriteStream 方法中的 write 方法将数据写入文件。现在我需要找到特定流的写入是否完成。我怎么能找到。
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.
每次写入完成时，我都需要调用其他方法。我该怎么做。
采纳答案by maerics
From the node.js WritableStream.write(...)documentationyou can give the "write" method a callback that is called when the written data is flushed:
从 node.jsWritableStream.write(...)文档中，您可以为“write”方法提供一个回调，在刷新写入的数据时调用该回调：
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.
请注意，在将下一个调用排队之前，您可能实际上不需要等待每个“写入”调用完成。即使“write”方法返回false，您仍然可以调用后续写入，节点会将挂起的写入请求缓冲到内存中。
回答by Hitesh Sahu
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 flagsyou can use.
我正在使用 maerics 的答案以及错误处理。该标志'a'用于打开文件进行追加。如果文件不存在，则创建该文件。您可以使用其他标志。
// 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();
