Response streaming middleware for Express 4.
npm install express-streamResponse streaming middleware for Express 4.
express-stream exposes two middleware functions.
* stream.pipe() is the least opinionated BigPipe implementation around and is ideal for client-side rendering
* stream.stream() is ideal for server-side rendering
Both methods allow you to get content in front of your users as fast as possible by taking forms of latency that generally occur sequentially and making them occur in parallel.
``javascript
//Requires
var express = require('express');
var ejs = require('ejs');
var stream = require('express-stream');
var superagent = require('superagent');
//App setup
var app = express();
app.set('views', './views');
app.set('view engine', 'ejs');
//Add the middleware to the desired routes
app.get('/', stream.pipe(), function (req, res) {
res.stream('landing'); //Stream the landing page
superagent
.get(uri)
.end(function (err, response){
res.stream('landing-data', {response.body.data}); //Stream data to populate the landing page
res.close();
}
);
});
`
This example would immediately stream 'landing' to the browser while the superagent call fatches the dynamic parts of the page. As soon as the superagent call resolves, it is streamed within a self-executing JavaScript block from which it injects some data into the already-rendered view.
`javascript
//Requires
var express = require('express');
var ejs = require('ejs');
var stream = require('express-stream');
//App setup
var app = express();
app.set('views', './views');
app.set('view engine', 'ejs');
//App-wide streaming setup
stream.useAllAutoTags(true);
stream.streamBefore('pre-body-view');
stream.streamAfter('post-body-view');
//Add the middleware to the desired routes
app.get('/', stream.stream(), function (req, res) {
res.render('landing'); //This route will now stream
});
`
This example streams the pre-body-layout view as soon as the stream.stream() middleware is run, and then landing and post-body-layout as soon as res.render() is called.
Because express-stream's two middleware functions patch express's res object differently, the API section is divided into two portions--one for each middleware function. Any functions you see within a section are only applicable when used with the middleware from the same portion of the API. stream.pipe()'s API is simpler so it's in a table. stream.stream()'s API is more complex so it's written out with examples.
| Function | Scope | Description | Arguments |
|---|---|---|---|---|
| stream.pipe() | middleware | This middleware function is written for client-side rendering. It can be used as a loose BigPipe implementation. | N/A |
|res.stream(view, options, callback) | res | When you use .pipe(), this funciton is added to the res object. It is the same as res.render() except that it does not close the HTTP connection. | Same as express |Output
| res.pipe(output, encoding) | res | Send a string of JavaScrpit to the client | : JavaScript output as a string Encoding: defaults to 'UTF-8' |res.pipe()
| res.close(output, encoding) | res | Same as , but closes the connection when finished. | Same as res.pipe() |res.pipe()
| stream.wrapJavascript(val) | stream | Whether to wrap all and res.close() output with '' | val: boolean stating whether to use this feature, defaults to false |
> _App-wide API Call_
Set an app-wide options object to be merged with the options param passed to all res.render() and res.stream() calls.
#### Arguments
* options: type: object, default: {}
> _App-wide API Call_
Set an app-wide view, or array of views, to stream as soon as the stream.stream() middleware is run. It's recommended that the views passed to .streamBefore() be used to open the and
tags and list site-wide dependencies.If
view is an array, all other passed params will be ignored.#### Arguments
* view: type: string || array of strings || array of objects
* options: same as express's
options param
* callback: same as express's callback param#### Examples
With
view as a string
`javascript
stream.streamBefore('global-head', {custom: data});
`With
as an array of strings
`javascript
stream.streamBefore(['global-head-one', 'global-head-two']);
`With
as an array of objects
`javascript
var globalHeadList = [
{view: 'global-head-one', options: {custom: data}},
{view: 'global-head-two'}
]
stream.streamBefore(globalHeadList);
`.streamAfter(view, options, callback)
> _App-wide API Call_
Set an app-wide view, or array of views, to stream as soon as the
call completes. It's recommended that the views passed to .streamAfter() be used to close the and tags.If
view is an array, all other passed params will be ignored.#### Arguments
* view: type: string || array of strings || array of objects
* options: same as express's
options param
* callback: same as express's callback param#### Examples
With
view as a string
`javascript
stream.streamAfter('global-footer', {custom: data});
`With
as an array of strings
`javascript
stream.streamAfter(['global-footer-one', 'global-footer-two']);
`With
as an array of objects
`javascript
var globalHeadList = [
{view: 'global-footer-one', options: {custom: data}},
{view: 'global-footer-two'}
]
stream.streamAfter(globalHeadList);
`.openHtmlOpenHead(view, options, callback)
> _App-wide API Call_
If
is true, this will simply stream a string to the client. If view is a string, this will stream the associated view with optional options and callback.#### Arguments
* view: boolean or string
* options: same as express's
options param
* callback: same as express's callback param.closeHeadOpenBody(view, options, callback)
> _App-wide API Call_
If
view is true, this will simply stream a string to the client. If view is a string, this will stream the associated view with optional options and callback.#### Arguments
* view: boolean or string
* options: same as express's
options param
* callback: same as express's callback param.closeBodyCloseHtml(view, options, callback)
> _App-wide API Call_
If
view is true, this will simply stream a string to the client. If view is a string, this will stream the associated view with optional options and callback.#### Arguments
* view: boolean or string
* options: same as express's
options param
* callback: same as express's callback param.useAllAutoTags(val)
> _App-wide API Call_
A convenience method to set the same boolean value for
openHtmlOpenHead, closeHeadOpenBody, and closeBodyCloseHtml in a single call.#### Arguments
* val: boolean or string
.stream(headView, headOptions, headCallback)
> _Middleware-only API Call_
Set an optional route-specific view, or list of views, to be rendered after the
.streamBefore() array and before any res.stream()/res.render() views. It's recommended that your .streamBefore() views not close the tag so that route-specific blocking dependencies can be injected into the here.If
headView is an array, all other passed params will be ignored.#### Arguments
* headView: type: string || array of strings || array of objects
* headOptions: same as express's
options param
* headCallback: same as express's callback param#### Examples
With
headView as a string`javascript
app.get('/stream-route', stream.stream('render-blocking-assets', {custom: data}), function (req, res){
res.render('stream-body');
});
`With
as an array of strings`javascript
app.get('/stream-route', stream.stream(['blocking-one', 'blocking-two']), function (req, res){
res.render('stream-body');
});
`With
as an array of objects`javascript
var blockingList = [
{view: 'blocking-one', options: {custom: data}},
{view: 'blocking-two'}
]
app.get('/stream-route', stream.stream(blockingList), function (req, res){
res.render('stream-body');
});
`res.render(view, options, callback)
> _Route-specific API Call_
Compiles and streams a view, then compiles and streams the views set by
, then closes the connection.#### Arguments
* All arguments are identical to
express's res.render() callres.stream(view, options, callback)
> _Route-specific API Call_
Compiles and streams a view just like
res.render(), but does not trigger the .streamAfter() array and does not close the connection.#### Arguments
* All arguments are identical to
express's res.render()` callUsage examples are coming. In the mean time, see this demo app.