Passing variables dynamically in a created Express.js route

Question

Passing variables dynamically in a created Express.js route

Creating routes in Express.js from a JSON file with the specified structure:

{
  "/home":{
    "token":"ksdjfglkas"
  },
  "/logout":{
    "token":"ksdjfglksaudhf"
  }
}

It is necessary to access the token within the routes function. The JavaScript code used for generating the route is as follows:

for(var endpoint in context){
  var route = context[endpoint];
  app.use(endpoint,
    function(req,res,next){
      req.token= route.token;
      next();
    },
    require('./route-mixin'));
}

The issue encountered is that the route-mixin method always receives the last token. In this case, 'context' refers to the JavaScript file mentioned above. How can different tokens be passed for each route individually.

javascript express

Answer 1

Answer №1

To solve this issue, I implemented a closure to encapsulate the content within the loop.

The problem was initially identified thanks to PhpStorm IDE: https://i.stack.imgur.com/4fQWz.png

Encountering the error message

mutable variable is accessible from closure

in the first middleware led me to seek guidance from this article Mutable variable is accessible from closure. How can I fix this?, suggesting the use of closures.

The simple resolution involved changing the code snippet from:

   for(var endpoint in context){
         var route = context[endpoint];
         app.use(endpoint,
             function (req, res, next) {
                 req.token = route.token;
                 next();
             },
             function (req, res) {
                 console.log(req.token);
                 res.send('test');
             }
         );
    }

to:

for(var endpoint in context){
    (function() {
        var route = context[endpoint];
        app.use(endpoint,
            function (req, res, next) {
                req.token = route.token;
                next();
            },
            function (req, res) {
                console.log(req.token);
                res.send('test');
            }
        );
    })();
}

The final example below demonstrates the functional solution that allowed the code to run successfully:

var express = require('express');
var app = express();

var context =  {
    "/home":{
        "token":"ksdjfglkas"
    },
    "/logout":{
        "token":"ksdjfglksaudhf"
    }
};
for(var endpoint in context){
    (function() {
        var route = context[endpoint];
        app.use(endpoint,
            function (req, res, next) {
                req.token = route.token;
                next();
            },
            function (req, res) {
                console.log(req.token);
                res.send('test');
            }
        );
    })();
}

app.listen(3000);

Answer 2

To solve this issue, I implemented a closure to encapsulate the content within the loop.

The problem was initially identified thanks to PhpStorm IDE: https://i.stack.imgur.com/4fQWz.png

Encountering the error message

mutable variable is accessible from closure

in the first middleware led me to seek guidance from this article Mutable variable is accessible from closure. How can I fix this?, suggesting the use of closures.

The simple resolution involved changing the code snippet from:

   for(var endpoint in context){
         var route = context[endpoint];
         app.use(endpoint,
             function (req, res, next) {
                 req.token = route.token;
                 next();
             },
             function (req, res) {
                 console.log(req.token);
                 res.send('test');
             }
         );
    }

to:

for(var endpoint in context){
    (function() {
        var route = context[endpoint];
        app.use(endpoint,
            function (req, res, next) {
                req.token = route.token;
                next();
            },
            function (req, res) {
                console.log(req.token);
                res.send('test');
            }
        );
    })();
}

The final example below demonstrates the functional solution that allowed the code to run successfully:

var express = require('express');
var app = express();

var context =  {
    "/home":{
        "token":"ksdjfglkas"
    },
    "/logout":{
        "token":"ksdjfglksaudhf"
    }
};
for(var endpoint in context){
    (function() {
        var route = context[endpoint];
        app.use(endpoint,
            function (req, res, next) {
                req.token = route.token;
                next();
            },
            function (req, res) {
                console.log(req.token);
                res.send('test');
            }
        );
    })();
}

app.listen(3000);

Passing variables dynamically in a created Express.js route

Answer №1

Similar questions

Utilize the datepicker function in jQuery version 1.6.3 to select a range of dates

Configure webpack to source the JavaScript file locally instead of fetching it through HTTP

Slider with Dual Images: A Visual Comparison

HapiJS commences an extended duration background process

In node.js, ensure that only JSON error messages are sent instead of HTML

The hosting service Heroku is currently having trouble recognizing the concurrent command within the "npm run start" script

Using Typescript in React to render font colors with specific styling

The Safari 7.1+ browser seems to be having trouble with the spotlight effect

Acquire the content of a nested element using jQuery

Mastering the art of grouping by a key and generating sub-objects from a plain array of key-value pairs in JavaScript ES5 without relying on third-party libraries

Executing Code Upon Module Load and Presenting It as Middleware

How do I test Pinia by calling one method that in turn calls another method, and checking how many times it has been called

Encountering a problem when trying to reference socket.io

Comparing Server Sent Events and Ajax with Websockets and Ajax

Exploring the Art of Navigation with Ionic and Angular

What is the best way to adjust the width of these elements for a perfect fit?

Execute sequential animations on numerous elements without using timeouts

Learn how to easily toggle table column text visibility with a simple click

Simple steps to add a click event listener to every element within a div

Prevent accordion expansion triggered by the More button click