blocks|key|246620|text|JavaScript是鸭子类型的，所以如果你只复制a+readable+stream's+API，它就会工作得很好。实际上，您可能不能实现这些方法中的大多数，或者只是将它们留为存根；您所需要实现的就是库使用的内容。您也可以使用Node预先构建的EventEmitter+class来处理事件，这样您就不必自己实现addListener之类的东西。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|246621|下面是如何在CoffeeScript中实现它：|246622|class+StringStream+extends+require('events').EventEmitter
++constructor:+(@string)+->+super()

++readable:+true
++writable:+false

++setEncoding:+->+throw+'not+implemented'
++pause:+->++++#+nothing+to+do
++resume:+->+++#+nothing+to+do
++destroy:+->++#+nothing+to+do
++pipe:+->+throw+'not+implemented'

++send:+->
++++@emit+'data',+@string
++++@emit+'end'|code-block|syntax|javascript|246623|然后你可以像这样使用它：|246624|stream+=+new+StringStream+someString
doSomethingWith+stream
stream.send()|246625|entityMap|0|LINK|mutability|MUTABLE|url|http://nodejs.org/api/stream.html#stream_readable_stream|1|http://nodejs.org/api/events.html#events_class_events_eventemitter^0|3E|C|4C|B|P|N|0|3E|I|1|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@$9|15|A|16|1|17]|$9|18|A|19|1|1A]]|E|$]]|$1|F|3|G|5|6|7|1B|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|1C|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1D|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|1E|8|@]|D|@]|E|$K|L]]|$1|Q|3|-4|5|6|7|1F|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]|Y|$5|T|U|V|E|$W|Z]]]]

JavaScript is duck-typed, so if you just copy <a href="http://nodejs.org/api/stream.html#stream_readable_stream" rel="nofollow">a readable stream's API</a>, it'll work just fine. In fact, you can probably not implement most of those methods or just leave them as stubs; all you'll need to implement is what the library uses. You can use Node's pre-built <a href="http://nodejs.org/api/events.html#events_class_events_eventemitter" rel="nofollow"><code>EventEmitter</code> class</a> to deal with events, too, so you don't have to implement <code>addListener</code> and such yourself.

Here's how you might implement it in CoffeeScript:



<pre><code>class StringStream extends require('events').EventEmitter
 constructor: (@string) -&gt; super()

 readable: true
 writable: false

 setEncoding: -&gt; throw 'not implemented'
 pause: -&gt; # nothing to do
 resume: -&gt; # nothing to do
 destroy: -&gt; # nothing to do
 pipe: -&gt; throw 'not implemented'

 send: -&gt;
 @emit 'data', @string
 @emit 'end'
</code></pre>

Then you could use it like so:

<pre><code>stream = new StringStream someString
doSomethingWith stream
stream.send()
</code></pre>

blocks|key|246647|text|只需创建一个新的stream模块实例，并根据需要对其进行自定义：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|246648|var+Stream+=+require('stream');
var+stream+=+new+Stream();

stream.pipe+=+function(dest)+{
++dest.write('your+string');
++return+dest;
};

stream.pipe(process.stdout);+//+in+this+case+the+terminal,+change+to+ya-csv|code-block|syntax|javascript|246649|或|246650|var+Stream+=+require('stream');
var+stream+=+new+Stream();

stream.on('data',+function(data)+{
++process.stdout.write(data);+//+change+process.stdout+to+ya-csv
});

stream.emit('data',+'this+is+my+string');|246651|entityMap^0|8|6|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|P|$]]

Just create a new instance of the <code>stream</code> module and customize it according to your needs:

<pre><code>var Stream = require('stream');
var stream = new Stream();

stream.pipe = function(dest) {
 dest.write('your string');
 return dest;
};

stream.pipe(process.stdout); // in this case the terminal, change to ya-csv
</code></pre>

or

<pre><code>var Stream = require('stream');
var stream = new Stream();

stream.on('data', function(data) {
 process.stdout.write(data); // change process.stdout to ya-csv
});

stream.emit('data', 'this is my string');
</code></pre>

blocks|key|463280|text|在咖啡脚本中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|463281|class+StringStream+extends+Readable
++constructor:+(@str)+->
++++super()

++_read:+(size)+->
++++@push+@str
++++@push+null|code-block|syntax|javascript|463282|使用它：|463283|new+StringStream('text+here').pipe(stream1).pipe(stream2)|463284|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

in coffee-script:

<pre><code>class StringStream extends Readable
 constructor: (@str) -&gt;
 super()

 _read: (size) -&gt;
 @push @str
 @push null
</code></pre>

use it:

<pre><code>new StringStream('text here').pipe(stream1).pipe(stream2)
</code></pre>

blocks|key|246745|text|有一个这样的模块：https://www.npmjs.com/package/string-to-stream|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|246746|var+str+=+require('string-to-stream')
str('hi+there').pipe(process.stdout)+//+=>+'hi+there'+|code-block|syntax|javascript|246747|entityMap|0|LINK|mutability|MUTABLE|url|https://www.npmjs.com/package/string-to-stream^0|9|1A|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

There's a module for that: <a href="https://www.npmjs.com/package/string-to-stream" rel="nofollow noreferrer">https://www.npmjs.com/package/string-to-stream</a>

<pre><code>var str = require('string-to-stream')
str('hi there').pipe(process.stdout) // =&gt; 'hi there' 
</code></pre>

blocks|key|463369|text|我厌倦了每六个月重新学习一次，所以我只是发布了一个npm模块来抽象出实现细节：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|463370|https://www.npmjs.com/package/streamify-string|offset|length|463371|这是模块的核心：|463372|const+Readable+=+require('stream').Readable;
const+util+++++=+require('util');

function+Streamify(str,+options)+{

++if+(!+(this+instanceof+Streamify))+{
++++return+new+Streamify(str,+options);
++}

++Readable.call(this,+options);
++this.str+=+str;
}

util.inherits(Streamify,+Readable);

Streamify.prototype._read+=+function+(size)+{

++var+chunk+=+this.str.slice(0,+size);

++if+(chunk)+{
++++this.str+=+this.str.slice(size);
++++this.push(chunk);
++}

++else+{
++++this.push(null);
++}

};

module.exports+=+Streamify;|code-block|syntax|javascript|463373|str是调用时必须传递给构造函数的string，它将由流作为数据输出。对于每个the+documentation，options是可以传递给流的典型选项。|style|CODE|463374|根据Travis+CI的说法，它应该与大多数版本的节点兼容。|463375|entityMap|0|LINK|mutability|MUTABLE|url|1|https://nodejs.org/api/stream.html#stream_new_stream_readable_options^0|0|0|1A|0|0|0|0|0|3|H|6|1L|7|13|H|1|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|12|8|@]|9|@$D|13|E|14|1|15]]|A|$]]|$1|F|3|G|5|6|7|16|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|17|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|18|8|@$D|19|E|1A|O|P]|$D|1B|E|1C|O|P]|$D|1D|E|1E|O|P]]|9|@$D|1F|E|1G|1|1H]]|A|$]]|$1|Q|3|R|5|6|7|1I|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|1J|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|C]]|Z|$5|V|W|X|A|$Y|10]]]]

I got tired of having to re-learn this every six months, so I just published an npm module to abstract away the implementation details:

<a href="https://www.npmjs.com/package/streamify-string" rel="noreferrer">https://www.npmjs.com/package/streamify-string</a>

This is the core of the module:

<pre><code>const Readable = require('stream').Readable;
const util = require('util');

function Streamify(str, options) {

 if (! (this instanceof Streamify)) {
 return new Streamify(str, options);
 }

 Readable.call(this, options);
 this.str = str;
}

util.inherits(Streamify, Readable);

Streamify.prototype._read = function (size) {

 var chunk = this.str.slice(0, size);

 if (chunk) {
 this.str = this.str.slice(size);
 this.push(chunk);
 }

 else {
 this.push(null);
 }

};

module.exports = Streamify;
</code></pre>

<code>str</code> is the <code>string</code> that must be passed to the constructor upon invokation, and will be outputted by the stream as data. <code>options</code> are the typical options that may be passed to a stream, per <a href="https://nodejs.org/api/stream.html#stream_new_stream_readable_options" rel="noreferrer">the documentation</a>.

According to Travis CI, it should be compatible with most versions of node.

blocks|key|463406|text|另一种解决方案是将read函数传递给Readable的构造函数(参见文档stream+readeable+options)|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|463407|var+s+=+new+Readable({read(size)+{
++++this.push("your+string+here")
++++this.push(null)
++}});|code-block|syntax|javascript|463408|您可以在使用s.pipe之后进行示例|463409|entityMap|0|LINK|mutability|MUTABLE|url|https://nodejs.org/api/stream.html#stream_new_stream_readable_options^0|10|O|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@]|C|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

Another solution is passing the read function to the constructor of Readable (cf doc <a href="https://nodejs.org/api/stream.html#stream_new_stream_readable_options" rel="noreferrer">stream readeable options</a>)

<pre><code>var s = new Readable({read(size) {
 this.push("your string here")
 this.push(null)
 }});
</code></pre>

you can after use s.pipe for exemple

blocks|key|246849|text|以下是TypeScript中的一个整洁的解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|246850|import+{+Readable+}+from+'stream'

class+ReadableString+extends+Readable+{
++++private+sent+=+false

++++constructor(
++++++++private+str:+string
++++)+{
++++++++super();
++++}

++++_read()+{
++++++++if+(!this.sent)+{
++++++++++++this.push(Buffer.from(this.str));
++++++++++++this.sent+=+true
++++++++}
++++++++else+{
++++++++++++this.push(null)
++++++++}
++++}
}

const+stringStream+=+new+ReadableString('string+to+be+streamed...')|code-block|syntax|javascript|246851|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Heres a tidy solution in TypeScript:

<pre><code>import { Readable } from 'stream'

class ReadableString extends Readable {
 private sent = false

 constructor(
 private str: string
 ) {
 super();
 }

 _read() {
 if (!this.sent) {
 this.push(Buffer.from(this.str));
 this.sent = true
 }
 else {
 this.push(null)
 }
 }
}

const stringStream = new ReadableString('string to be streamed...')
</code></pre>

blocks|key|463495|text|从节点10.17开始，stream.Readable有一个from方法，可以轻松地从任何可迭代对象(包括数组文字)创建流：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|463496|const+{+Readable+}+=+require("stream")

const+readable+=+Readable.from(["input+string"])

readable.on("data",+(chunk)+=>+{
++console.log(chunk)+//+will+be+called+once+with+`"input+string"`
})|code-block|syntax|javascript|463497|请注意，至少在10.17和12.3之间，字符串本身是可迭代的，因此Readable.from("input+string")将起作用，但会为每个字符发出一个事件。Readable.from(["input+string"])将为数组中的每一项(在本例中为一项)发出一个事件。|463498|还要注意，在以后的节点中(可能是12.3，因为文档中说函数当时已更改)，不再需要将字符串包装在数组中。|463499|https://nodejs.org/api/stream.html#stream_stream_readable_from_iterable_options|463500|entityMap|0|LINK|mutability|MUTABLE|url^0|T|4|0|0|X|T|29|V|0|0|0|27|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|10|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|11|8|@$9|12|A|13|B|C]|$9|14|A|15|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|16|8|@]|D|@]|E|$]]|$1|O|3|P|5|6|7|17|8|@]|D|@$9|18|A|19|1|1A]]|E|$]]|$1|Q|3|-4|5|6|7|1B|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|P]]]]

From node 10.17, stream.Readable have a <code>from</code> method to easily create streams from any iterable (which includes array literals):

<pre><code>const { Readable } = require("stream")

const readable = Readable.from(["input string"])

readable.on("data", (chunk) =&gt; {
 console.log(chunk) // will be called once with `"input string"`
})
</code></pre>

Note that at least between 10.17 and 12.3, a string is itself a iterable, so <code>Readable.from("input string")</code> will work, but emit one event per character. <code>Readable.from(["input string"])</code> will emit one event per item in the array (in this case, one item).

Also note that in later nodes (probably 12.3, since the documentation says the function was changed then), it is no longer necessary to wrap the string in an array.

<a href="https://nodejs.org/api/stream.html#stream_stream_readable_from_iterable_options" rel="noreferrer">https://nodejs.org/api/stream.html#stream_stream_readable_from_iterable_options</a>

I am using a library, <a href="https://github.com/koles/ya-csv">ya-csv</a>, that expects either a file or a stream as input, but I have a string.

How do I convert that string into a stream in Node?

How to create streams from string in Node.Js?

TypeScript

我使用的是一个名为的库，它需要一个文件或流作为输入，但我有一个字符串。如何在Node中将该字符串转换为流？

问如何在Node.Js中从字符串创建流？
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问如何在Node.Js中从字符串创建流？EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问如何在Node.Js中从字符串创建流？
EN