hacky google apps script invert colors script .js

function onOpen() {
  const ui = DocumentApp.getUi();
  // Or DocumentApp or FormApp.
  ui.createAddonMenu()
      .addItem('Invert Selected', 'doInvertSelected')
      .addToUi();
}

function invertColor(val) {
  return '#' + ('00000' + (0xFFFFFF - parseInt(val.substr(1), 16)).toString(16)).substr(-6);
}

function doInvertSelected() {
  const doc = DocumentApp.getActiveDocument();
  const selection = doc.getSelection();
  if (!selection)
    return;
  
  const rangeElements = selection.getRangeElements();
  for (const rangeElement of rangeElements) {
    const element = rangeElement.getElement();
    rinvert(element);
  }
}

function rinvert(element) {
  if (element.getNumChildren) {
    console.log(element.getNumChildren());
    for (let i = 0; i < element.getNumChildren(); i++) {
      rinvert(element.getChild(i));
    }
    return;
  }
  
  const oldStyle = element.getAttributes();
  const oldBackground = oldStyle[DocumentApp.Attribute.BACKGROUND_COLOR];
  
  const style = {};
  if (oldBackground) {
    style[DocumentApp.Attribute.BACKGROUND_COLOR] = invertColor(oldBackground);
  }
  element.setAttributes(style);
  
  if (element.getForegroundColor) {
    for (let i = 0; i < element.getText().length; i++) {
      element.setForegroundColor(i, i, invertColor(element.getForegroundColor(i)));
    }
  }
}