Replace <input/> tag with <textarea/> tag to preserve line-breaks.

replaceInputWithTextarea.js

/**
 * Convert <input/> to <textarea/> to preserve line-breaks.
 */
function replaceInputWithTextarea(input) {
  if (input.type !== 'text') return;

  // Create textarea element.
  const textarea = document.createElement('textarea');

  // Copy all input attributes except `value`.
  [].slice.apply(input.attributes).forEach(({nodeName, nodeValue}) => {
    if (nodeName !== 'value') {
      textarea.setAttribute(nodeName, nodeValue);
    } else {
      // Copy input value to textarea content.
      textarea.innerHTML = nodeValue;
    }
  });

  // Replace input tag.
  input.replaceWith(textarea);
}