discourse/app/assets/javascripts/pretty-text/censored-words.js.es6

export function censor(text, censoredWords) {
  if (censoredWords && censoredWords.length) {
    const split = censoredWords.split("|");
    let censorRegexp;
    if (split && split.length) {
      censorRegexp = new RegExp("(\\b(?:" + split.map(function (t) { return "(" + t.replace(/[-/\\^$*+?.()|[\]{}]/g, '\\$&') + ")"; }).join("|") + ")\\b)(?![^\\(]*\\))", "ig");
    }

    if (censorRegexp) {
      let m = censorRegexp.exec(text);
      while (m && m[0]) {
        const replacement = new Array(m[0].length+1).join('■');
        text = text.replace(new RegExp("(\\b" + m[0] + "\\b)(?![^\\(]*\\))", "ig"), replacement);
        m = censorRegexp.exec(text);
      }
    }
  }
  return text;
}