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# eventsource-parser
[](https://www.npmjs.com/package/eventsource-parser)[](https://bundlephobia.com/result?p=eventsource-parser)[](https://www.npmjs.com/package/eventsource-parser)
A streaming parser for [server-sent events/eventsource](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events), without any assumptions about how the actual stream of data is retrieved. It is intended to be a building block for clients and polyfills in javascript environments such as browsers, node.js and deno.
You create an instance of the parser, and _feed_ it chunks of data - partial or complete, and the parse emits parsed messages once it receives a complete message. A [TransformStream variant](#stream-usage) is also available for environments that support it (modern browsers, Node 18 and higher).
## Installation
```bash
npm install --save eventsource-parser
```
## Usage
```ts
import {createParser, type ParsedEvent, type ReconnectInterval} from 'eventsource-parser'
function onParse(event: ParsedEvent | ReconnectInterval) {
if (event.type === 'event') {
console.log('Received event!')
console.log('id: %s', event.id || '<none>')
console.log('name: %s', event.name || '<none>')
console.log('data: %s', event.data)
} else if (event.type === 'reconnect-interval') {
console.log('We should set reconnect interval to %d milliseconds', event.value)
}
}
const parser = createParser(onParse)
const sseStream = getSomeReadableStream()
for await (const chunk of sseStream) {
parser.feed(chunk)
}
// If you want to re-use the parser for a new stream of events, make sure to reset it!
parser.reset()
console.log('Done!')
```
## Stream usage
```ts
import {EventSourceParserStream} from 'eventsource-parser/stream'
const eventStream = response.body
.pipeThrough(new TextDecoderStream())
.pipeThrough(new EventSourceParserStream())
```
Note that the TransformStream is exposed under a separate export (`eventsource-parser/stream`), in order to maximize compatibility with environments that do not have the `TransformStream` constructor available.
## License
MIT © [Espen Hovlandsdal](https://espen.codes/)
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