├── package.json ├── README.md ├── lib └── sse.ts └── LICENSE /package.json: -------------------------------------------------------------------------------- 1 | { 2 | "name": "sse-ts", 3 | "version": "1.0.3", 4 | "description": "A ES6-based flexible Server-Sent Events source; supports GET and POST requests and custom headers to a SSE endpoint", 5 | "main": "./lib/sse.ts", 6 | "scripts": { 7 | "test": "echo \"Error: no test specified\" && exit 1" 8 | }, 9 | "repository": { 10 | "type": "git", 11 | "url": "https://github.com/smartmuki/sse-ts" 12 | }, 13 | "keywords": [ 14 | "sse", 15 | "server-side-events", 16 | "server-sent-events", 17 | "eventsource", 18 | "sse-ts", 19 | "sse-es6" 20 | ], 21 | "publishConfig": { 22 | "registry":"https://registry.npmjs.org/" 23 | }, 24 | "author": "Mukesh Agarwal ", 25 | "license": "Apache-2.0", 26 | "bugs": { 27 | "url": "https://github.com/smartmuki/sse-ts/issues" 28 | }, 29 | "homepage": "https://github.com/smartmuki/sse-ts" 30 | } 31 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # sse-ts 2 | 3 | Forked from `https://github.com/mpetazzoni/sse.js`. 4 | Made the library strongly typed and added support for ES6 modules. So this library can now be imported as a ES6 module and compiled with TS. 5 | 6 | `sse-ts` is a strongly-typed ES6 module-based flexible `EventSource` replacement for Typescript designed 7 | to consume Server-Sent Events (SSE) streams with more control and 8 | options than the standard `EventSource`. The main limitations of 9 | `EventSource` are that it only supports no-payload GET requests, and 10 | does not support specifying additional custom headers to the HTTP 11 | request. This library solves the problem by providing: 12 | - Support for GET and POST requests to a SSE endpoint 13 | - Support for additional headers that can be passed 14 | - Support for `withCredentials` flag 15 | 16 | 17 | ## Installation 18 | ```ts 19 | npm i sse-ts 20 | ``` 21 | OR 22 | ```ts 23 | yarn add sse-ts 24 | ``` 25 | 26 | ## Basic usage 27 | 28 | The most simple way to use `SSE` is to create the `SSE` object, attach 29 | one or more listeners, and activate the stream: 30 | 31 | ```ts 32 | 33 | import { CustomEventDataType, CustomEventType, SSE, SSEOptions, SSEOptionsMethod } from "sse-ts"; 34 | 35 | const sseOptions: SSEOptions = { 36 | method: SSEOptionsMethod.GET 37 | }; 38 | 39 | 40 | const source = new SSE(backendURL, sseOptions); 41 | source.addEventListener('message', (event: CustomEventType) => { 42 | const dataEvent = event as CustomEventDataType; 43 | // Assuming we receive JSON-encoded data payloads: 44 | var payload = JSON.parse(dataEvent.data); 45 | console.log(payload); 46 | }); 47 | 48 | source.stream(); 49 | ``` 50 | 51 | ## Events 52 | 53 | `SSE` implements the `EventTarget` interface (just like `EventSource`) 54 | and emits fully constructed `Event` objects. The type of the event 55 | corresponds to the Server-Sent Event's _name_, and the event's timestamp 56 | is the UNIX timestamp of the _reception_ of the event. 57 | 58 | Additionally, the events will have the following fields if the event type is `CustomEventDataType`: 59 | 60 | - `id`: the event ID, if present; `null` otherwise 61 | - `data`: the event data, unparsed 62 | 63 | `SSE`, like `EventSource`, will emit the following events: 64 | 65 | - `open`, when the first block of data is received from the event 66 | stream; 67 | - `error`, if an error occurs while making the request; 68 | - `readystatechange`, to notify of a change in the ready state of the 69 | event source. 70 | 71 | Note that all events dispatched by `SSE` will have the event target 72 | initially set to the `SSE` object itself. 73 | 74 | ## Listening for specific event types 75 | 76 | The [Server-Sent Events 77 | specification](https://html.spec.whatwg.org/multipage/comms.html#server-sent-events) 78 | allows for arbitrary event types, as the `event` field of the event. The 79 | default event type is `message`, so you'll most likely want to register 80 | a listener for this kind of events. If you expect another type of 81 | events, simply register your callback with the appropriate event type: 82 | 83 | ```ts 84 | import { CustomEventDataType, CustomEventType, SSE, SSEOptions, SSEOptionsMethod } from "sse-ts"; 85 | 86 | const sseOptions: SSEOptions = { 87 | method: SSEOptionsMethod.GET 88 | }; 89 | 90 | const source = new SSE(backendURL, sseOptions); 91 | source.addEventListener('status', (event: CustomEventType) => { 92 | const dataEvent = event as CustomEventDataType; 93 | console.log('System status is now: ' + dataEvent.data); 94 | }); 95 | 96 | source.stream(); 97 | ``` 98 | 99 | 100 | ## Passing custom headers 101 | 102 | ```ts 103 | import { CustomEventDataType, CustomEventType, SSE, SSEOptions, SSEOptionsMethod } from "sse-ts"; 104 | 105 | const sseOptions: SSEOptions = { 106 | headers: { 'Content-Type': 'application/json', 'api-key': "apiKey" }, 107 | method: SSEOptionsMethod.GET, 108 | }; 109 | 110 | const source = new SSE(backendURL, sseOptions); 111 | 112 | ``` 113 | 114 | ## Making a POST request and overriding the HTTP method 115 | 116 | To make a HTTP POST request, simply specify a `payload` in the options: 117 | 118 | ```ts 119 | import { CustomEventDataType, CustomEventType, SSE, SSEOptions, SSEOptionsMethod } from "sse-ts"; 120 | 121 | const sseOptions: SSEOptions = { 122 | headers: { 'Content-Type': 'application/json', 'api-key': "apiKey" }, 123 | method: SSEOptionsMethod.POST, 124 | payload: JSON.stringify({ 125 | foo: "bar" 126 | }) 127 | }; 128 | 129 | const source = new SSE(backendURL, sseOptions); 130 | ``` 131 | 132 | 133 | ## `withCredentials` support 134 | 135 | This `EventSource` polyfill supports the `withCredentials` option to 136 | request that the outgoing HTTP request be made with a CORS credentials 137 | mode of `include`, as per the [HTML Living 138 | Standard](https://fetch.spec.whatwg.org/#concept-request-credentials-mode). 139 | 140 | ## Options reference 141 | 142 | | Name | Description | 143 | | ----------------- | ----------- | 144 | | `headers` | A map of additional headers to use on the HTTP request | 145 | | `method` | (Required) Override HTTP method (GET or POST) | 146 | | `payload` | The request payload to sent with the request | 147 | | `withCredentials` | If set to `true`, CORS requests will be set to include credentials | 148 | 149 | ## TODOs and caveats 150 | 151 | - Internet Explorer 11 does not support arbitrary values in 152 | `CustomEvent`s. A dependency on `custom-event-polyfill` is necessary 153 | for IE11 compatibility. 154 | - Improve `XmlHttpRequest` error handling and connection states 155 | - Automatically reconnect with `Last-Event-ID` 156 | -------------------------------------------------------------------------------- /lib/sse.ts: -------------------------------------------------------------------------------- 1 | /** 2 | * Copyright (C) 2021 Mukesh Agarwal 3 | * All rights reserved. 4 | */ 5 | 6 | /** 7 | * Copyright (C) 2016 Maxime Petazzoni . 8 | * All rights reserved. 9 | */ 10 | 11 | const FIELD_SEPARATOR = ':'; 12 | 13 | enum XHRStates { 14 | INITIALIZING = -1, 15 | CONNECTING = 0, 16 | OPEN = 1, 17 | CLOSED = 2 18 | } 19 | 20 | export type CustomEventReadyStateChangeType = CustomEvent & { 21 | readyState: XHRStates 22 | } 23 | 24 | export type CustomEventErrorType = CustomEvent & { 25 | reason: Event; 26 | } 27 | 28 | export type CustomEventDataType = CustomEvent & { 29 | data: any; // Represents a JSON object 30 | id: string; 31 | }; 32 | 33 | export enum SSEOptionsMethod { 34 | GET = "GET", 35 | POST = "POST" 36 | } 37 | 38 | export type CustomEventType = CustomEvent | CustomEventDataType | CustomEventReadyStateChangeType | CustomEventErrorType; 39 | 40 | export interface SSEOptions { 41 | /** 42 | * A dictionary of key-value pairs. 43 | * Like: { "Content-type": "application/json" } 44 | */ 45 | headers?: {[key: string]: string} 46 | 47 | /** 48 | * The XMLHttpRequest.withCredentials property is a boolean value 49 | * that indicates whether or not cross-site Access-Control requests 50 | * should be made using credentials such as cookies, 51 | * authorization headers or TLS client certificates. 52 | * Setting withCredentials has no effect on same-site requests. 53 | */ 54 | withCredentials?: boolean; 55 | 56 | /** 57 | * The HTTP method (currently only GET and POST are supported) 58 | * [Required]. 59 | */ 60 | method: SSEOptionsMethod; 61 | 62 | /** 63 | * The JSON stringified payload representing the request body. 64 | */ 65 | payload?: string; 66 | } 67 | 68 | export type Callback = (e: CustomEventType) => void; 69 | 70 | export class SSE { 71 | private listeners: {[key: string]: Callback[]} = {}; 72 | private readyState: XHRStates = XHRStates.INITIALIZING; 73 | private chunk = ''; 74 | private progress = 0; 75 | private xhr: XMLHttpRequest | null = null; 76 | 77 | constructor(private url: string, private options: SSEOptions) { 78 | if (!url) { 79 | throw new Error("url cannot be null"); 80 | } 81 | 82 | if (!options || !options.method) { 83 | throw new Error("Method is mandatory in `options`"); 84 | } 85 | } 86 | 87 | public addEventListener(type: string, listener: Callback): void { 88 | this.listeners[type] = this.listeners[type] || []; 89 | 90 | if (this.listeners[type].indexOf(listener) === -1) { 91 | this.listeners[type].push(listener); 92 | } 93 | } 94 | 95 | public removeEventListener(type: string, listener: Callback) { 96 | if (!this.listeners[type]) { 97 | return; 98 | } 99 | 100 | const filteredListeners = this.listeners[type].filter(lis => lis !== listener); 101 | if (!filteredListeners.length) { 102 | delete this.listeners[type]; 103 | } else { 104 | this.listeners[type] = filteredListeners; 105 | } 106 | } 107 | 108 | public stream() { 109 | this._setReadyState(XHRStates.CONNECTING); 110 | 111 | this.xhr = new XMLHttpRequest(); 112 | this.xhr.onreadystatechange = evt => this._checkStreamClosed(evt); 113 | this.xhr.onprogress = evt => this._onStreamProgress(evt); 114 | this.xhr.onload = evt => this._onStreamLoaded(evt); 115 | this.xhr.onerror = evt => this._onStreamFailure(evt); 116 | this.xhr.onabort = evt => this._onStreamFailure(evt); 117 | 118 | this.xhr.open(this.options.method, this.url); 119 | 120 | for (const header in this.options.headers) { 121 | this.xhr.setRequestHeader(header, this.options.headers[header]); 122 | } 123 | 124 | this.xhr.withCredentials = !!this.options.withCredentials; 125 | this.xhr.send(this.options.payload); 126 | }; 127 | 128 | close() { 129 | if (this.readyState === XHRStates.CLOSED) { 130 | return; 131 | } 132 | 133 | if(this.xhr) { 134 | this.xhr.abort(); 135 | } 136 | this.xhr = null; 137 | this._setReadyState(XHRStates.CLOSED); 138 | }; 139 | 140 | private dispatchEvent(e: CustomEventType | null) { 141 | if (!e) { 142 | return true; 143 | } 144 | 145 | // e.source = this; Dont expose the SSE object 146 | 147 | const onHandler = 'on' + e.type; 148 | if (this.hasOwnProperty(onHandler)) { 149 | (this as any)[onHandler].call(this, e); 150 | if (e.defaultPrevented) { 151 | return false; 152 | } 153 | } 154 | 155 | if (this.listeners[e.type]) { 156 | return this.listeners[e.type].every((callback: Callback) => { 157 | callback(e); 158 | return !e.defaultPrevented; 159 | }); 160 | } 161 | 162 | return true; 163 | }; 164 | 165 | private _setReadyState(state: XHRStates) { 166 | const event = new CustomEvent('readystatechange') as CustomEventReadyStateChangeType; 167 | event.readyState = state; 168 | this.readyState = state; 169 | this.dispatchEvent(event); 170 | }; 171 | 172 | _onStreamFailure(e: Event) { 173 | const failureEvent = new CustomEvent('error') as CustomEventErrorType; 174 | failureEvent.reason = e; 175 | this.dispatchEvent(failureEvent); 176 | this.close(); 177 | } 178 | 179 | _onStreamProgress(e: Event) { 180 | if (!this.xhr) { 181 | return; 182 | } 183 | 184 | if (this.xhr.status >= 400) { 185 | this._onStreamFailure(e); 186 | return; 187 | } 188 | 189 | if (this.readyState === XHRStates.CONNECTING) { 190 | const openEvent = new CustomEvent('open'); 191 | this.dispatchEvent(openEvent); 192 | this._setReadyState(XHRStates.OPEN); 193 | } 194 | 195 | const data = this.xhr.responseText.substring(this.progress); 196 | this.progress += data.length; 197 | 198 | data.split(/(\r\n|\r|\n){2}/g).forEach((part: string) => { 199 | if (part.trim().length === 0) { 200 | const chunkEvent = this._parseEventChunk(this.chunk.trim()); 201 | this.dispatchEvent(chunkEvent); 202 | this.chunk = ''; 203 | } else { 204 | this.chunk += part; 205 | } 206 | }); 207 | }; 208 | 209 | private _onStreamLoaded(e: Event) { 210 | this._onStreamProgress(e); 211 | 212 | const streamData = this._parseEventChunk(this.chunk); 213 | 214 | // Parse the last chunk. 215 | this.dispatchEvent(streamData); 216 | this.chunk = ''; 217 | }; 218 | 219 | /** 220 | * Parse a received SSE event chunk into a constructed event object. 221 | */ 222 | private _parseEventChunk(chunk: string) { 223 | if (!chunk || !chunk.length) { 224 | return null; 225 | } 226 | 227 | const e: any = { 'id': null, 'retry': null, 'data': '', 'event': 'message' }; 228 | 229 | chunk.split(/\n|\r\n|\r/).forEach((line: string) => { 230 | line = line.trimRight(); 231 | const index = line.indexOf(FIELD_SEPARATOR); 232 | if (index <= 0) { 233 | // Line was either empty, or started with a separator and is a comment. 234 | // Either way, ignore. 235 | return; 236 | } 237 | 238 | const field = line.substring(0, index); 239 | if (!(field in e)) { 240 | return; 241 | } 242 | 243 | const value = line.substring(index + 1).trimLeft(); 244 | if (field === 'data') { 245 | e[field] += value; 246 | } else { 247 | e[field] = value; 248 | } 249 | }); 250 | 251 | const event = new CustomEvent(e.event) as CustomEventDataType; 252 | event.data = e.data; 253 | event.id = e.id; 254 | return event; 255 | }; 256 | 257 | private _checkStreamClosed(_e: Event) { 258 | if (!this.xhr) { 259 | return; 260 | } 261 | 262 | if (this.xhr.readyState === XMLHttpRequest.DONE) { 263 | this._setReadyState(XHRStates.CLOSED); 264 | } 265 | }; 266 | }; -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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