I have a simple html page being served by express on a node.js server and in the client side javascript i want to access some server side variables. I tried googling around for a solution but didn't see a straight forward solution without using some sort of templating engine.

So if i need to access a variable on the server from a client side JS served from the same host, what do i need to do?

I have a simple html page being served by express on a node.js server and in the client side javascript i want to access some server side variables. I tried googling around for a solution but didn't see a straight forward solution without using some sort of templating engine.

So if i need to access a variable on the server from a client side JS served from the same host, what do i need to do?

• javascript
• node.js
• express

• Output json to the document in a script tag, or make an AJAX request for the data. – elclanrs Commented Mar 2, 2016 at 21:34
• Like @elclanrs said, output javascript between script tags in your document, use AJAX or - as a third option - use socket.io for realtime munication. – Sébastien Vercammen Commented Mar 2, 2016 at 21:35
• Personally websockets are the way to go here. I hate having an express route setup to literally return a single variable. Being able to just send data over at anytime is just so much easier than all those xhr calls. – Sterling Archer Commented Mar 2, 2016 at 21:38
• Using some sort of templating that access res.locals, either EJS, Jade or something you create yourself, is usually a good thing, and makes it easy to transfer data to the HTML at pageload without any additional requests. – adeneo Commented Mar 2, 2016 at 22:12

4 Answers 4

To access the variable on the client, you'll need to expose it inside of a script tag, there are a few node modules that can help you with it (ex: express-state) https://www.npmjs./package/express-state, but you'll need a templating engine to generate the html required for it. You can use a variety of templating engines when working with express. If you use express generators straight out of the box it should e with jade and you can use different options on the generators to use other templating engines. See here for express generator options http://expressjs./en/starter/generator.html

Create an API to expose your variable:

app.get('/myvar', function(req, res){
  res.send(varYouWantToSend);
 });

Then in the client-side make a call for that API with a http GET request. The url for the API would be www.yoursite./myvar in this example.

You could try using this lib:

https://github./siriusastrebe/syc

and if you want to implement yourself look into Ajax. Jquery have a pretty simple ajax wrapper (http://api.jquery./jquery.ajax/). offcourse you need to open corresponding urls on the server to return / set the values.

Try socket.io http://socket.io/ it uses websockets on modern browsers and gracefully degradate to older technologies like AJAX with older browsers, leaving user experience the same.

Check out details here Web Socket support in Node.js/Socket.io for older browser