How can I catch a rendering error / missing template in node.js using express.js?

Question

I have code like this that will render a jade template without a route defined. Think of this like the express.static but it calls res.render with the url.

app.use(function (req, res, next) {
    try {
        res.render(req.url.substring(1), { title: "No Controller", user: req.session.user });
    } catch (err) {
        console.log(err)
        next();
    }
});

The problem is that res.render() isn't throwing an error. Instead it is rendering an error page. Is there a way to detect a missing template or any rendering errors?

respectTheCode · Accepted Answer · 2015-07-20 14:34:31Z

49

A better way to do it, instead of requiring fs and having another callback, would be to use render's callback :

res.render(my_page_im_not_sure_it_exists, {}, function(err, html) {
    if(err) {
        res.redirect('/404'); // File doesn't exist
    } else {
        res.send(html);
    }
});

edited Jul 20, 2015 at 14:34

respectTheCode

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answered Mar 28, 2013 at 18:44

Augustin Riedinger

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7 Comments

respectTheCode Over a year ago

Great find. Its only in 3.x docs but it works in 2.x as well.

Codebling Over a year ago

Updated answer to use res.send instead of res.end. 4.x documentation specifically states "If you need to respond with data, instead use methods such as res.send()"

Codebling Over a year ago

I thought this would generate a 404 if there was an error processing the template, but it doesn't seem to. Anyone care to explain why it does not?

Augustin Riedinger Over a year ago

A 404 code is what your server wants to reply to a request to tell the querying browser conventionnaly that the page was not found. At this step, you are the server, and you are free to reply with whatever you want. If you want to send a 404 error instead of redirecting the the /404 url, the correct way to do this is here.

Sebastian Nielsen Over a year ago

What does the second argument in 'render' indicate? I am talking about the "{}" after "my_page_im_not_sure_it_exists"

|

respectTheCode · Accepted Answer · 2013-02-04 18:40:45Z

2

Use fs.exists(p, [callback]) to check if the file exists before calling res.render

http://nodejs.org/docs/latest/api/fs.html#fs_fs_exists_path_callback

Node 0.6.x and older

Use path.exists(p, [callback]) to check if the file exists before calling res.render

http://nodejs.org/docs/v0.6.0/api/path.html#path.exists

edited Feb 4, 2013 at 18:40

answered Sep 13, 2011 at 23:58

respectTheCode

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1 Comment

SomeKittens Over a year ago

With the latest (0.8.x) version of node, you should use fs.exists()

Wtower · Accepted Answer · 2016-01-10 18:56:33Z

1

Similar to @Augustin Riedinger's answer, the same applies when rendering to variable using renderFile:

var html = jade.renderFile('path/to/file.jade', context, function(err, html) {};

answered Jan 10, 2016 at 18:56

Wtower

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Comments

generalhenry · Accepted Answer · 2011-09-05 14:49:49Z

0

You could use fs.open to check if the template exists.

app.use(function (req, res, next) {
    fs.open(__dirname + '/views/' + req.url.substring(1) + '.jade', 'r', function (err) {
      if(err) {
        console.log(err);
        return next();
      }
      res.render(req.url.substring(1), { title: "No Controller", user: req.session.user });
    }
});

answered Sep 5, 2011 at 14:49

generalhenry

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1 Comment

respectTheCode Over a year ago

res.render has a bunch of logic for figuring out what jade file to use. I was hoping that I wouldn't need to recreate that logic.

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