index.js

const postRequest = require('./helper/util.js');

const clickHandler = document.querySelector('.clickHandler');
const outputField = document.querySelector('input[name=response]');
const inputString = document.querySelector('input[name=request]');

const updateInputField = () => {
  postRequest(inputString.value).then(res => {
    outputField.value = res.body;
    inputString.value = '';
  });
};

const changeDisplayMsg = () => {
  clickHandler.textContent = 'Enter anything!!';
};

const changeDisplayMsgBack = () => {
  clickHandler.textContent = 'I will sort your string!';
};

clickHandler.addEventListener('mouseenter', () => changeDisplayMsg());
clickHandler.addEventListener('mouseleave', () => changeDisplayMsgBack());
clickHandler.addEventListener('click', () => updateInputField());

document.addEventListener('keypress', event => {
  if (event.key == 'Enter') updateInputField();
});