login.js

function login() {
  if (checker()) {
    axios
    .post('/api/login', {
      username: username.value,
      password: password.value
    })
    .catch(function (error) {
      console.log(error);
      alert(error)
    })
    .then(function (response) {
      if (response.data.token) {
        alert('token:'+response.data.token+'\nid:'+ response.data.user_id)
        window.location.href = '/';
      } else {
        alert(response.data)
      }
    })
  }
}