script.js

setInterval(function() {
	let chat = document.getElementsByClassName('_1mf _1mj');
	console.log(chat)
  // make sure chat window exists
  if (chat.length>0){
		for(i = 0; i<chat.length; i++){
			emojify(chat[i.toString()]);
		}
  } else {
    // console.log("No chat windows open")
  }

}, 1000);

function emojify(chat_box) {
		let text = chat_box.textContent;
		// make sure user has typed something
		if(text.length > 1){
			let start = text.indexOf(":")+1;
			// check for starting ':'
			if(start > 0) {
				let end = text.indexOf(":", start);
				// check for ending ':'
				if(end > 0) {
					let emoji_alias = text.slice(start, end);
					// Make sure emoji doesnt have whitespace
					if(/^\S*$/.test(emoji_alias)){
							console.log("emoji requested: "+emoji_alias+"\nstarts: "+start+"\nends:"+end);
							// console.log(getMeAnEmoji(emoji_alias))
							let converted = text.substring(0, start-1)+getMeAnEmoji(emoji_alias)+text.substring(end+1)
							// console.log("final: "+converted)
							chat_box.textContent = converted;
					}
				}
			}
		} else {
			// console.log("Found an empty chat window")
		}
}

/** SOURCE CODE FROM: https://github.com/notwaldorf/emoji-translate **/
var allEmojis;
var SYMBOLS = '!"#$%&\'()*+,-./:;<=>?@[]^_`{|}~';

(function() {
  var request = new XMLHttpRequest();
  request.open('GET', chrome.extension.getURL('/emojis.json'), true);
  request.onload = function() {
    if (request.status >= 200 && request.status < 400) {
      allEmojis = JSON.parse(request.response);
    }
  };
  request.send();
})();

function getMeAnEmoji(keyword) {
  keyword = keyword.trim().toLowerCase();

  if (!keyword || keyword === '' || keyword === 'it')
    return '';

  // Maybe this is a plural word but the keyword is the singular?
  var maybeSingular = '';
  if (keyword[keyword.length - 1] == 's')
    maybeSingular = keyword.slice(0, keyword.length - 1);

  // Maybe this is a singular word but the keyword is the plural?
  // Don't do this for single letter since that will pluralize crazy things.
  var maybePlural = (keyword.length == 1) ? '' : keyword + 's';

  // Go through all the things and find the first one that matches.
  for (var emoji in allEmojis) {
    var keywords = allEmojis[emoji].keywords;
    if (emoji == keyword || emoji == maybeSingular || emoji == maybePlural ||
        (keywords && keywords.indexOf(keyword) >= 0) ||
        (keywords && keywords.indexOf(maybeSingular) >= 0) ||
        (keywords && keywords.indexOf(maybePlural) >= 0))
      return allEmojis[emoji].char;
  }
  return '';
};

/** END OF SOURCE CODE FROM: https://github.com/notwaldorf/emoji-translate **/