<form onSubmit={this.handleLogin.bind(this)} action="/" method="post">
    <div>
        <label>Username:</label>
        <input type="text" name="username"/>
    </div>
    <div>
        <label>Password:</label>
        <input type="password" name="password"/>
    </div>
    <div>
        <input type="submit" value="Log In"/>
    </div>
</form>

handleLogin(){
    fetch('http://localhost:8080', {
        method: 'post',
       body: JSON.stringify({
         username: this.state.username,
         password: this.state.password

      })
   })

}

app.post('/', function(req, res, next) {
    console.log("post");
    passport.authenticate('register', function(err, user, info) {
        console.log("authenticate");
    })(req, res, next);
});