The beginning of a Chrome Extension to add markdown on http://twitter.com

script.js

/*
@TODO :
- Add italic-bold
- Change the .tweet-counter value
*/

!function(window, document) {
    // From http://mothereff.in/twitalics
    var types = {
            // `new Number` is needed since we want to add properties to the numbers later (cache)
            'italic': new Number(0xddc1)
          , 'bold': new Number(0xdd8d)
          , 'italic-bold': new Number(0xddf5)
        }

    function replace(string, lowercaseCode, type) {
        return string.replace(/[a-zA-Z]/g, function(character) {
                var charCode = character.charCodeAt()
                  , isUppercase = charCode < 97
                  , typeRef = types[type]
                return typeRef[character] || (typeRef[character] = String.fromCharCode(0xd835, charCode + lowercaseCode + (isUppercase ? 6 : 0)))
            })
    }


/*
    doc.addEventListener('input', function(e) {
        var el = e.target

        if (el.classList.contains('twitter-anywhere-tweet-box-editor')) {
            var count = el.value.length
            el.value = el.value.replace(/(\*\*|__)(?=\S)([^\r]*?\S[*_]*)\1/g, function(match, osef, word) {
                count -= 4
            }).replace(/(\*|_)(?=\S)([^\r]*?\S)\1/g, function(match, osef, word) {
                count -= 2
            })
            console.log(count)
        }
    })
 */

    // The click on the button
    doc.addEventListener('click', function(e) {
        var el = e.target

        if (el.classList.contains('tweet-button')) {
            var textarea = el.parentElement.parentElement.parentElement.querySelector('.twitter-anywhere-tweet-box-editor')
            textarea.value = textarea.value.replace(/(\*\*|__)(?=\S)([^\r]*?\S[*_]*)\1/g, function(match, osef, word) {
                return replace(word, types.bold, 'bold')
            }).replace(/(\*|_)(?=\S)([^\r]*?\S)\1/g, function(match, osef, word) {
                return replace(word, types.italic, 'italic')
            })
        }
    }, true)
}(this, doc)