Node.js 可写流完成事件
当所有数据都被刷新到隐藏系统时,可写流中的“完成”事件在调用 writable.end() 方法后发出。
句法:
Event: 'finish'
返回值:如果之前调用了 writable.end() 方法,则发出此事件,否则不发出。
下面的示例说明了 Node.js 中“完成”事件的使用:
示例 1:
// Node.js program to demonstrate the
// finish event
// Including 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');
// Calling end function
writable.end();
// Emitting finish event
writable.on('finish', function() {
console.log("Write is completed.");
});
// Displays that the program
// is ended
console.log("program is ended.");
输出:
hi
program is ended.
Write is completed.
在上面的例子中, writeable.end() 方法在完成事件之前被调用,所以它被发出。
示例 2:
// Node.js program to demonstrate the
// finish event
// Including 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');
// Emitting finish event
writable.on('finish', function() {
console.log("Write is completed.");
});
// Displays that the program
// is ended
console.log("program is ended.");
输出:
hi
program is ended.
因此,此处未调用 writable.end()函数,因此未执行完成事件。
参考: https://nodejs.org/api/stream.html#stream_event_finish