Quick function to use in dev tools to improve reading experience on old HTML articles/papers

set-reader-style.js

/**
 *  Gives the browser window a better midly altered reading view for
 *  pages that use unaltered styles for margin, etc. Limits line length,
 *  slightly reduces contrast, increases line height. Great for old HTML
 *  formatted research papers.
 *
 *  @param {number?} level - Set the level of the contrast. Defaults to 0.
 *  @returns {boolean} - True if the function succeeds, false if not.
 */
function setReaderStyles(level = 0) {
  const setLevel = level || 0; // Older browsers
  
  const levels = [
    {
      "level": 0,
      "backgroundColor": "rgb(245, 245, 245)",
      "color": "#444",
    },
  ];
  
  if (setLevel > (levels.length - 1) || setLevel < 0))
      throw new Error("Level not within range");

  if (!document)
      throw new Error("Not a browser");
  if (!document.body)
      throw new Error("Body element not found"); // Don't support too-old browsers
  try {
    document.body.style.maxWidth = "70%";
    document.body.style.marginLeft = "15%";
    document.body.style.lineHeight = 1.3;
  
    document.body.style.backgroundColor = levels[setLevel]["backgroundColor"];
    document.body.style.color = levels[setLevel]["color"];
  } catch (e) {
    
    return false;
  }
  
  return true;
}