[Aetae]

Если вариант выше не поможет, попробуй так, для надёжности):

function setValue(element, value, options) {
  if(typeof element === 'string') 
    element = document.querySelector(element);

  options = Object.assign({
    bubbles: true
  }, options);

  element.dispatchEvent(new Event('focus', options));
  element.dispatchEvent(new Event('keydown', options));
  element.dispatchEvent(new Event('keypress', options));
  
  element.value = value;
  
  element.dispatchEvent(new Event('input', options));
  element.dispatchEvent(new Event('keyup', options));
  element.dispatchEvent(new Event('change', options));
  element.dispatchEvent(new Event('blur', options));

  return element;
}


setValue(document.querySelectorAll('input')[3], 'New Value')