Migrating Express.js 2 to 3, specifically app.dynamicHelpers() to app.locals.use?

Question

Updated Express.js from version 2 to 3, and the following call to app.dynamicHelpers({..}) broke as it is no longer present in V3:

app.dynamicHelpers({

    request: function(req){
      return req
    },
    ...etc.
});

There's a migration guide which says this:

app.dynamicHelpers() (use middleware + res.locals)

But I'm stumped how to do that. Is there a more concrete example of how to migrate that?

Related SO post: nodejs express 3.0

score 29 · Accepted Answer · answered Jul 26 '12 at 20:02

I had the same problem with session.user and just fixed it by understanding that the app.use function needs to be IN the configure part, not where it was before.

Before:

app.configure();
app.dynamicHelpers({
  user: function(req, res) {
    return req.session.user;
  }
});

After:

app.configure(function(){
  //...
  app.use(function(req, res, next){
    res.locals.user = req.session.user;
    next();
  });
  //...
});

for Flash have a look at connect-flash

score 6 · Answer 2 · edited May 23 '17 at 11:45

6

The solution with 16 votes is correct but be sure to use the res.locals assignment before app.use(app.router); refer to this post https://stackoverflow.com/a/12597730/1132109

edited May 23 '17 at 11:45

Community

1
1

answered Jun 19 '13 at 19:14

D4tech

83
1
4

score 3 · Answer 3 · answered Jul 20 '12 at 15:59

Have a look at the examples folder at github. For example auth:

app.use(function(req, res, next){
  var err = req.session.error,
      msg = req.session.success;
  delete req.session.error;
  delete req.session.success;
  res.locals.message = '';
  if (err) res.locals.message = '<p class="msg error">' + err + '</p>';
  if (msg) res.locals.message = '<p class="msg success">' + msg + '</p>';
  next();
});

You can then use the variable "message" in your template.

score 3 · Answer 4 · answered Jul 20 '12 at 17:03

reponse.locals.use is a new useful feature of Express that lets you send a variable to your model that first needs to be evaluated. Say, for example, you want to send 3 variables to your view, all of which have to come after a request to a mongodb. The "old" way was to nest 3 callbacks, and when the last one returned you would render your view. locals.use makes this a heck of a lot easier as it will evaluate your functions and will render your view only when all have been evaluated.

Here's a short snippet of code on how to use them (this is coffee-script, hopefully you can convert it to javascript :D)

response.locals.use (request, response, done) ->
    myAsynchMethod (value) ->
        reponse.locals.myProperty = value
        done()

In this case, there will be a variable named myProperty you can use on your view that has it's value set to whatever myAsynchMethod gave the callback.

where would you use response.local.use? is it defined in the app.js or in the route hanlder(req,res)->..if so when to call the render... — coool, Apr 13 '13 at 12:16

Migrating Express.js 2 to 3, specifically app.dynamicHelpers() to app.locals.use?

4 Answers4

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