express-stream

Response streaming middleware for Express 4.

What is This?

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.

Basic Client-Side Render/BigPipe Usage

//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.

Basic Server-Side Render Usage

//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.

API

A note about the API section

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.

stream.pipe()

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
res.pipe(output, encoding)	res	Send a string of JavaScrpit to the client	`Output`: JavaScript output as a string `Encoding`: defaults to 'UTF-8'
res.close(output, encoding)	res	Same as `res.pipe()`, but closes the connection when finished.	Same as `res.pipe()`
stream.wrapJavascript(val)	stream	Whether to wrap all `res.pipe()` and `res.close()` output with ''	`val`: boolean stating whether to use this feature, defaults to false

stream.stream()

.globalOptions(options)

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: {}

.streamBefore(view, options, callback)

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 <html> and <head> 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

stream.streamBefore('global-head', {custom: data});

With view as an array of strings

stream.streamBefore(['global-head-one', 'global-head-two']);

With view as an array of objects

var globalHeadList = [
  {view: 'global-head-one', options: {custom: data}},
  {view: 'global-head-two'}
]
stream.streamBefore(globalHeadList);

.streamAfter(view, options, callback)

Set an app-wide view, or array of views, to stream as soon as the res.render() call completes. It's recommended that the views passed to .streamAfter() be used to close the <body> and <html> 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

stream.streamAfter('global-footer', {custom: data});

With view as an array of strings

stream.streamAfter(['global-footer-one', 'global-footer-two']);

With view as an array of objects

var globalHeadList = [
  {view: 'global-footer-one', options: {custom: data}},
  {view: 'global-footer-two'}
]
stream.streamAfter(globalHeadList);

.openHtmlOpenHead(view, options, callback)

If view is true, this will simply stream a <!doctype html><html><head> 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)

If view is true, this will simply stream a </head><body> 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)

If view is true, this will simply stream a </body></html> 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)

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)

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 <head> tag so that route-specific blocking dependencies can be injected into the <head> 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

app.get('/stream-route', stream.stream('render-blocking-assets', {custom: data}), function (req, res){
  res.render('stream-body');
});

With headView as an array of strings

app.get('/stream-route', stream.stream(['blocking-one', 'blocking-two']), function (req, res){
  res.render('stream-body');
});

With headView as an array of objects

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)

Compiles and streams a view, then compiles and streams the views set by .streamAfter(), then closes the connection.

Arguments

All arguments are identical to express's res.render() call

res.stream(view, options, callback)

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() call

More!

Usage examples are coming. In the mean time, see this demo app.

express-stream

express-stream

What is This?

Basic Client-Side Render/BigPipe Usage

Basic Server-Side Render Usage

API

A note about the API section

stream.pipe()

stream.stream()

.globalOptions(options)

Arguments

.streamBefore(view, options, callback)

Arguments

Examples

.streamAfter(view, options, callback)

Arguments

Examples

.openHtmlOpenHead(view, options, callback)

Arguments

.closeHeadOpenBody(view, options, callback)

Arguments

.closeBodyCloseHtml(view, options, callback)

Arguments

.useAllAutoTags(val)

Arguments

.stream(headView, headOptions, headCallback)

Arguments

Examples

res.render(view, options, callback)

Arguments

res.stream(view, options, callback)

Arguments

More!

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