如何使用express 3.x在node.js中的EJS模板中包含js文件

Question

All the examples I am seeing use the app.dynamicHelpers to provide a method for accessing my javascript files in my view templates. But in express 3.x there is no clear way to do this. The migration docs say "use middleware". I'm relatively new to the concept of 'middleware' and don't know how to implement this.

All I would like to know is the most elegant way to include javascript files in my view templates.

Answer 1

Middleware is the foundation to Connect , which Express is built upon. In short, it allows you to chain together multiple handlers of an incoming HTTP request and response. The argument you provide to each app.use() in your Express application is basically a "middleware" and is a callback with the following signature function (request, response, next) , where next is the next middleware callback to call in the chain. All the below are middleware (the last being an error handler which has a 4 parameter signature):

app.use(express.bodyParser());
app.use(express.methodOverride());
app.use(app.router);
app.use(function(err, req, res, next){
  // logic
  next();
});

In terms of the move from Express 2 to 3.x, the migration is specifically:

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

So, with a contrived example, where you may have previously had a helper function in an external js file and require d it for use in your dynamicHelper :

//helpers.js
exports.dynamicHelpers = {
  currentUser: function(req, res) {
    return req.user;
  }
};

// app.js
var helpers = require('./helpers').dynamicHelpers;

app.dynamicHelpers(helpers);

With a bit of reorganization you could now do something like:

//locals.js
exports.setLocals = function(req, res, next){ //<- middleware function
  res.locals.currentUser = req.user;
  res.locals.otherVariable = ...;
  next();
}

//app.js
var locals = require('./locals').setLocals;
...
app.use(locals);

This is a good blog with a review of middleware vs. dynamicHelpers in pre-3.x Express, but the concepts are the same. The only difference being that res.local(name, value) used in the article is now deprecated for res.locals.name = value or res.locals({ name: value })