new stream.Duplex(options)
-
options
<Object> 传给Writable
和Readable
构造函数。还有以下字段:¥
options
<Object> Passed to bothWritable
andReadable
constructors. Also has the following fields:-
allowHalfOpen
<boolean> 如果设置为false
,则流将在可读端结束时自动结束可写端。默认值:true
。¥
allowHalfOpen
<boolean> If set tofalse
, then the stream will automatically end the writable side when the readable side ends. Default:true
. -
readable
<boolean> 设置Duplex
是否可读。默认值:true
。¥
readable
<boolean> Sets whether theDuplex
should be readable. Default:true
. -
writable
<boolean> 设置Duplex
是否可写。默认值:true
。¥
writable
<boolean> Sets whether theDuplex
should be writable. Default:true
. -
readableObjectMode
<boolean> 为流的可读端设置objectMode
。如果objectMode
为true
,则无效。默认值:false
。¥
readableObjectMode
<boolean> SetsobjectMode
for readable side of the stream. Has no effect ifobjectMode
istrue
. Default:false
. -
writableObjectMode
<boolean> 为流的可写端设置objectMode
。如果objectMode
为true
,则无效。默认值:false
。¥
writableObjectMode
<boolean> SetsobjectMode
for writable side of the stream. Has no effect ifobjectMode
istrue
. Default:false
. -
readableHighWaterMark
<number> 为流的可读端设置highWaterMark
。如果提供highWaterMark
,则无效。¥
readableHighWaterMark
<number> SetshighWaterMark
for the readable side of the stream. Has no effect ifhighWaterMark
is provided. -
writableHighWaterMark
<number> 为流的可写端设置highWaterMark
。如果提供highWaterMark
,则无效。¥
writableHighWaterMark
<number> SetshighWaterMark
for the writable side of the stream. Has no effect ifhighWaterMark
is provided.
-
const { Duplex } = require('node:stream');
class MyDuplex extends Duplex {
constructor(options) {
super(options);
// ...
}
}
或者,当使用 ES6 之前的样式构造函数时:
¥Or, when using pre-ES6 style constructors:
const { Duplex } = require('node:stream');
const util = require('node:util');
function MyDuplex(options) {
if (!(this instanceof MyDuplex))
return new MyDuplex(options);
Duplex.call(this, options);
}
util.inherits(MyDuplex, Duplex);
或者,使用简化的构造函数方法:
¥Or, using the simplified constructor approach:
const { Duplex } = require('node:stream');
const myDuplex = new Duplex({
read(size) {
// ...
},
write(chunk, encoding, callback) {
// ...
},
});
使用管道时:
¥When using pipeline:
const { Transform, pipeline } = require('node:stream');
const fs = require('node:fs');
pipeline(
fs.createReadStream('object.json')
.setEncoding('utf8'),
new Transform({
decodeStrings: false, // Accept string input rather than Buffers
construct(callback) {
this.data = '';
callback();
},
transform(chunk, encoding, callback) {
this.data += chunk;
callback();
},
flush(callback) {
try {
// Make sure is valid json.
JSON.parse(this.data);
this.push(this.data);
callback();
} catch (err) {
callback(err);
}
},
}),
fs.createWriteStream('valid-object.json'),
(err) => {
if (err) {
console.error('failed', err);
} else {
console.log('completed');
}
},
);