I have a simple regex that should match words made of letters (0-5) only however it doesn't seems to be working. How should the regex look and be used in ExpressJS? URL I am trying to validate may look like something/abcd

var express = require("express"),
    app = express();

app.get("/:id(^[a-z]{0,5}$)", function(req, res) {
    res.send("The right path!");
});

app.listen(8000);

I have a simple regex that should match words made of letters (0-5) only however it doesn't seems to be working. How should the regex look and be used in ExpressJS? URL I am trying to validate may look like something./abcd

var express = require("express"),
    app = express();

app.get("/:id(^[a-z]{0,5}$)", function(req, res) {
    res.send("The right path!");
});

app.listen(8000);

• javascript
• regex
• node.js
• express

3 Answers 3

To set up an URL which accepts / followed by up to five ascii characters, you could do like this:

var express = require("express"),
app = express();

app.get("/[a-z]{0,5}$", function(req, res){
    res.send("Right path!");
});
app.listen(8000);

result:

GET http://localhost:8000/
Right path!

GET http://localhost:8000/abcde
Right path!

GET http://localhost:8000/abcdef
Cannot GET /abcdef

Note: Express does case insensitive routing by default. To change it, put this at the top of your script:

app.set('case sensitive routing', true);

Now, [a-z] will match only lower case characters: GET /abc but not GET /ABC

To make things clear: The original question is the valid syntax to match an express.js route in a

NAMED paramter

The only error is to have the start/end anchors within the RegExp. I think they are added automatically.

A nice tool to validate express routes says this is fine:

/:id([a-z]{0,5})

btw: To whoever downvoted the question: shame on you.

I would strongly suggest to use the "named param" syntax because app.param is a nice feature.

I don't know what app.get does, but if we are speaking about regular expressions:

^ can be situated at the first position. It means that need to pare string from beginning. Or, in [^\d] block, this means inversion, in this case this is any symbol except number.

remove ^ symbol