Login.jsx

import React, { Component } from "react";

export default class LoginForm extends Component {
  state = {
    username: "",
    password: ""
  };

  handleSubmit = e => {
    e.preventDefault();
    console.log("Submitted");
  };

  handleChange = input => e => {
    this.setState({
      [input]: e.target.value
    });
  };

  render() {
    const { username, password } = this.state;
    return (
      <div>
        <h1>Login</h1>
        <form onSubmit={this.handleSubmit}>
          <div className="form-group">
            <label htmlFor="username">Username</label>
            <input
              value={username}
              name="username"
              onChange={this.handleChange("username")}
              id="username"
              type="text"
              className="form-control"
            />
          </div>
          <div className="form-group">
            <label htmlFor="password">Password</label>
            <input
              value={password}
              name="password"
              onChange={this.handleChange("password")}
              id="password"
              type="password"
              className="form-control"
            />
          </div>
          <button className="btn btn-primary">Login</button>
        </form>
      </div>
    );
  }
}