word_filter.js

// ==UserScript==
// @name              Word Filter
// @description       Replace words with other words.
// @namespace         http://daliwa.li
// @include           *
// @version           1.0.0
// @grant             none
// ==/UserScript==


'use strict';


// word filter, where keys are regular expressions
const wordFilter = {
  'Suzy Bao': '♥ Waifu Bao ♥',
  'suzyOcean': '♥ waifuOcean ♥',
  'raumkraehe': '♥ raumschwein ♥'
};


// x=============================x
// | do not edit below this line |
// x=============================x


init();


function init () {
  var node;
  var walk = document.createTreeWalker(
    document.body, NodeFilter.SHOW_TEXT, null, false);

  var mutationFilter = new MutationObserver(function (mutations) {
    mutations.forEach(mutationHandler);
  });

  // first walk the initial state of the DOM
  while (node = walk.nextNode()) {
    replaceWords(node);
  }

  // then observe changes on the DOM
  mutationFilter.observe(document.body, {
    childList: true,
    characterData: true,
    subtree: true
  });
}


function mutationHandler (mutation) {
  var i;
  var node;
  var walk;

  if (mutation.type === 'childList') {
    for (i = 0; i < mutation.addedNodes.length; i++) {
      node = mutation.addedNodes[i];
      if (node.nodeType === 1) {
        walk = document.createTreeWalker(
          node, NodeFilter.SHOW_TEXT, null, false);
        while (node = walk.nextNode()) {
          replaceWords(node);
        }
      } else if (node.nodeType === 3) {
        replaceWords(node);
      }
    }
  } else if (mutation.type === 'characterData') {
    replaceWords(mutation.target);
  }
}


function replaceWords (node) {
  var key;
  var regExp;

  for (key in wordFilter) {
    regExp = new RegExp('(\\b|^)' + key + '(\\b|$)', 'ig');
    (node.nodeValue.match(regExp) || []).forEach(function(match) {
      node.nodeValue = node.nodeValue.replace(match, function (value) {
        return replaceValue(value, wordFilter[key]);
      });
    });
  }
}


function replaceValue (value, replacement) {
  var firstCharacter = value.charAt(0);

  if (firstCharacter === firstCharacter.toLowerCase()) {
    replacement = replacement.charAt(0).toLowerCase() + replacement.slice(1);
  }

  else if (firstCharacter === firstCharacter.toUpperCase()) {
    replacement = replacement.charAt(0).toUpperCase() + replacement.slice(1);

    if (value === value.toUpperCase()) {
      replacement = replacement.toUpperCase();
    }
  }

  return replacement;
}