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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,87 @@ | ||
| section | ||
| h3(id='app.use') app.use([path], function) | ||
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| p. | ||
| Use the given middleware <code>function</code>, with optional mount <code>path</code>, | ||
| defaulting to "/". | ||
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| +js. | ||
| var express = require('express'); | ||
| var app = express(); | ||
|
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| // simple logger | ||
| app.use(function(req, res, next){ | ||
| console.log('%s %s', req.method, req.url); | ||
| next(); | ||
| }); | ||
|
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| // respond | ||
| app.use(function(req, res, next){ | ||
| res.send('Hello World'); | ||
| }); | ||
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| app.listen(3000); | ||
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| p. | ||
| The "mount" path is stripped and is <strong>not</strong> visible | ||
| to the middleware <code>function</code>. The main effect of this feature is that | ||
| mounted middleware may operate without code changes regardless of its "prefix" | ||
| pathname. | ||
|
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| p. | ||
| Here's a concrete example, take the typical use-case of serving files in ./public | ||
| using the <code>express.static()</code> middleware: | ||
|
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||
| +js. | ||
| // GET /javascripts/jquery.js | ||
| // GET /style.css | ||
| // GET /favicon.ico | ||
| app.use(express.static(__dirname + '/public')); | ||
|
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| p. | ||
| Say for example you wanted to prefix all static files with "/static", you could | ||
| use the "mounting" feature to support this. Mounted middleware functions are <strong>not</strong> | ||
| invoked unless the <code>req.url</code> contains this prefix, at which point | ||
| it is stripped when the function is invoked. This affects this function only, | ||
| subsequent middleware will see <code>req.url</code> with "/static" included | ||
| unless they are mounted as well. | ||
|
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||
| +js. | ||
| // GET /static/javascripts/jquery.js | ||
| // GET /static/style.css | ||
| // GET /static/favicon.ico | ||
| app.use('/static', express.static(__dirname + '/public')); | ||
|
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| p. | ||
| The order of which middleware are "defined" using <code>app.use()</code> is | ||
| very important, they are invoked sequentially, thus this defines middleware | ||
| precedence. For example usually <code>express.logger()</code> is the very | ||
| first middleware you would use, logging every request: | ||
|
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||
| +js. | ||
| app.use(express.logger()); | ||
| app.use(express.static(__dirname + '/public')); | ||
| app.use(function(req, res){ | ||
| res.send('Hello'); | ||
| }); | ||
|
|
||
| p. | ||
| Now suppose you wanted ignore logging requests for static files, but to | ||
| continue logging routes and middleware defined after <code>logger()</code>, | ||
| you would simply move <code>static()</code> above: | ||
|
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||
| +js. | ||
| app.use(express.static(__dirname + '/public')); | ||
| app.use(express.logger()); | ||
| app.use(function(req, res){ | ||
| res.send('Hello'); | ||
| }); | ||
|
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| p. | ||
| Another concrete example would be serving files from multiple directories, | ||
| giving precedence to "./public" over the others: | ||
|
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| +js. | ||
| app.use(express.static(__dirname + '/public')); | ||
| app.use(express.static(__dirname + '/files')); | ||
| app.use(express.static(__dirname + '/uploads')); |
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