[javascript] Put request with simple string as request body

This works for me (code called from node js repl):

const axios = require("axios");

axios
    .put(
        "http://localhost:4000/api/token", 
        "mytoken", 
        {headers: {"Content-Type": "text/plain"}}
    )
    .then(r => console.log(r.status))
    .catch(e => console.log(e));

Logs: 200

And this is my request handler (I am using restify):

function handleToken(req, res) {
    if(typeof req.body === "string" && req.body.length > 3) {
        res.send(200);
    } else {
        res.send(400);
    }
}

Content-Type header is important here.