Redirect all trailing slashes globally in express

Question

I am using Node.js and Express and I have the following routing :

app.get('/', function(req,res){
    locals.date = new Date().toLocaleDateString();

    res.render('home.ejs', locals);
});

function lessonsRouter (req, res, next)
{
    var lesson = req.params.lesson;
    res.render('lessons/' + lesson + '.ejs', locals_lessons);
}

app.get('/lessons/:lesson*', lessonsRouter);


function viewsRouter (req, res, next)
{
    var controllerName = req.params.controllerName;
    res.render(controllerName + '.ejs', locals_lessons);
}
app.get('/:controllerName', viewsRouter);

I have a Disqus widget on my lessons pages and I have noticed a strange behavior that when going to myapp.com/lessons and myapp.com/lessons/ I get two different pages (on of them had a comment I previously added in Disqus and the other one doesn't have a comment).

Is there a way to "canonize" all of my urls to be without trailing slashes ? I have tried to add the strict routing flag to express but the results were the same

Thanks

Answer 1

Try adding a middleware for that;

app.use((req, res, next) => {
  const test = /\?[^]*\//.test(req.url);
  if (req.url.substr(-1) === '/' && req.url.length > 1 && !test)
    res.redirect(301, req.url.slice(0, -1));
  else
    next();
});

Answer 2

The answer by Tolga Akyüz is inspiring but doesn't work if there is any characters after the slash. For example http://example.com/api/?q=a is redirected to http://example.com/api instead of http://example.com/api?q=a.

Here is an improved version of the proposed middleware that fix the problem by adding the original query to the end of the redirect destination url:

app.use(function(req, res, next) {
    if (req.path.substr(-1) == '/' && req.path.length > 1) {
        var query = req.url.slice(req.path.length);
        res.redirect(301, req.path.slice(0, -1) + query);
    } else {
        next();
    }
});

Note: As noted by jamesk and stated in RFC 1738, the trailing slash can only be omitted when there is nothing after the domain. Therefore, http://example.com?q=a is an invalid url where http://example.com/?q=a is a valid one. In such case, no redirection should be done. Fortunately, the expression req.path.length > 1 takes care of that. For example, given the url http://example.com/?q=a, the path req.path equals to / and thus the redirection is avoided.

Answer 3

The connect-slashes middleware was designed specifically for this need: https://npmjs.org/package/connect-slashes

Install it with:

$ npm install connect-slashes

Read the full documentation: https://github.com/avinoamr/connect-slashes

Answer 4

I'm adding this answer because I had too many issues with other solutions.

router.use(function(req, res, next) {
    if (req.originalUrl != req.baseUrl + req.url) {
        res.redirect(301, req.baseUrl + req.url);
    }
    else
        next();
});

This will translate:

/page ==> /page/
/page?query=value ==> /page/?query=value

Answer 5

One liner:

router.get('\\S+\/$', function (req, res) {
  return res.redirect(301, req.path.slice(0, -1) + req.url.slice(req.path.length));
});

This will only catch the url's that need to be redirected, and ignore the others.

Example results:

/         ==> /
/a        ==> /a
/a/       ==> /a
/a/b      ==> /a/b
/a/b/     ==> /a/b
/a/b/?c=d ==> /a/b?c=d

Answer 6

The answers above will work in a lot of cases but GET vars can encounter issues and if you were to put that inside another express middleware its reliance on req.path will cause a problem and its reliance on req.url can also have unwanted side effects. If you're looking for a tighter solution this will do the trick:

// Redirect non trailing slash to trailing slash
app.use(function(req, res, next){
    // Find the query string
    var qsi = req.originalUrl.indexOf('?');
    // Get the path
    var path = req.originalUrl;
    if(qsi > -1) path = path.substr(0, qsi);
    // Continue if the path is good or it's a static resource
    if(path.substr(-1) === '/' || ~path.indexOf('.')) return next();
    // Save just the query string
    var qs = '';
    if(qsi > -1) qs = req.originalUrl.substr(qsi);
    // Save redirect path
    var redirect = path + '/' + qs;
    // Redirect client
    res.redirect(301, redirect);

    console.log('301 redirected ' + req.originalUrl + ' to ' + redirect);
});

It's always happy with GET variables and won't break if you were to put it inside middleware.