express route, check if req.params parameter is empty

Question

I'm new to node and express and I would appreciate any help. I'm trying to write a get request which checks if the req.params.address_line is empty and does something if it is, but can't seem to figure out how to do that. So far I have tried this:

app.get('/smth/smth_else/:address_line', function(req, res){
  if(req.params.address_line===""){
    res.send("Hello World.")
  }
}

This isn't working though so I don't think it is correct. How can I check if the address_line is empty? I googled it extensively, but can't find a working solution. Thanks!

I guess you're looking for an optional path parameter, try: /smth/smth_else/:address_line? (note the ? at the end). — luukvhoudt
– luukvhoudt, Commented Oct 1, 2021 at 18:47

Sarfraaz talat · Accepted Answer · 2020-01-26 02:24:19Z

11

You'll have to check first if the whole req.params exists or not

Like this

app.get('/smth/smth_else/:address_line', function(req, res){

  if(!req.params)
    return res.send("NO PARAMS PASSED")

  if(!req.params.address_line)
    return res.send("NO address_line PASSED")

  if(req.params.address_line === ""){
    res.send("ADDRESS LINE EMPTY.")
  } else {
    res.send("ADDRESS LINE > ",req.params.address_line)
  }
}

answered Jan 26, 2020 at 2:24

Sarfraaz talat

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1 Comment

luukvhoudt Over a year ago

GET /smth/smth_else would result in a 404. Thus this request handler will only trigger res.send("ADDRESS LINE > ",req.params.address_line)

dillon · Accepted Answer · 2020-01-26 04:19:34Z

A potential option is to write a middleware that could create a nice reusable interface for requiring parameters like so:

const requireParams = params => (req, res, next) => {
    const reqParamList = Object.keys(req.params);
    const hasAllRequiredParams = params.every(param =>
        reqParamList.includes(param)
    );
    if (!hasAllRequiredParams)
        return res
            .status(400)
            .send(
                `The following parameters are all required for this route: ${params.join(", ")}`
            );

    next();
};

app.get("/some-route", requireParams(["address_line", "zipcode"]), (req, res) => {
    const { address_line, zipcode } = req.params;
    if (address_line === "") return res.status(400).send("`address_line` must not be an empty string");


    // continue your normal request processing...
});

This example makes use of express middlewares and Array.prototype.every(). If you are unfamiliar, these links will provide the relevant documentation for how this works.

Kevin Reilly · Accepted Answer · 2020-01-26 02:24:05Z

2

You can use a simple falsy check !req.params.address_line for when it is an empty string "", false, null, undefined, 0, or NaN.

answered Jan 26, 2020 at 2:24

Kevin Reilly

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1 Comment

dillon Over a year ago

It's important to be careful with just checking for falsey values if 0 is a valid value for the parameter. It might be better to explicitly check for param === undefined

Nagaraj Jayaraman · Accepted Answer · 2020-04-16 18:28:08Z

1

There are two cases, you need to handle

For unique route names

app.get('/smth/smth_else/:address_line', function(req, res){
  if(!req.params){
     res.send("Params Empty!")
  }
}

For duplicate route names and multiple params

app.get('/smth/smth_else/:address_line1/:address_line2', function(req, res){
  if(Object.keys(req.params).length === 0){
     res.send("Params Empty")
  }
}

edited Apr 16, 2020 at 18:28

answered Apr 16, 2020 at 18:20

Nagaraj Jayaraman

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