Unable to handle the errors in node.js

Question

I am new to node.js. I am trying incorporate error handling in the below code. I need to throw the error if I am not passing the parameter. One is if the tag parameter is empty another one is if I am not finding the tag field in the collection while passing.

case 1:

{ "likes" : 970
  "share" : 345
  "tag" : ""
} // throw error

case 2:

{
"likes" : 970
 "share" : 345
} // throw error

app.get('/api/ping/:tag', (req,res) => {    
    const dept = req.params.tag;
    console.log(dept)
    if(!dept) {
        res.json({error: "Provide Tag parameter to search"})
    } else {
        const blogData = blogPosts.filter((d) => d.tag == dept)[0];
        res.status(200).send({ok:true, blogData})
    }    
})

Can anyone help me on this