trans.js

var DICT_URL = 'http://oaadonline.oxfordlearnersdictionaries.com/dictionary/';
var TRANS_REGEXP = /<span class="phon-us".*?>.*?(<span class="flapped_t">.*?<\/span>.*?)*<\/span>/m;
document.addEventListener('dblclick',
    function(event)
        {
                var sel  = document.getSelection();
                var word = sel.toString().trim();
                var r = new XMLHttpRequest();
                r.open('GET', DICT_URL + word, false);
                r.send();
                var t = TRANS_REGEXP.exec(r.responseText)[0].replace(/<.*?>/g, '');
                sel.anchorNode.data = sel.anchorNode.data.replace(new RegExp(word,'gi'), t);
        }
);