Converts strings as ':heart:' to <span> elements with the equivalent emoji image in background. See http://www.emoji-cheat-sheet.com/

emojify.js

function emojify (domElement, ressource, size) {
    var element = document.getElementById(domElement)
    var matching = element.innerHTML.match(/:[a-z0-9+_-]+:/g)
    for (var i = matching.length - 1; i >= 0; i--) {
        element.innerHTML = element.innerHTML.replace(matching[i], '<span style="display:inline-block;background-image:url('+ressource+matching[i].slice(1, matching[i].length - 1)+'.png);background-size:'+size+'px;height:'+size+'px;width:'+size+'px;vertical-align:-10%;"></span>')
    }
}