https://addons.mozilla.org/ko/firefox/addon/naver-endic/

main.js

/**
 *
 * It's under MPL 1.1
 * See http://www.mozilla.org/MPL/1.1/
 * You can install this from https://addons.mozilla.org/ko/firefox/addon/naver-endic/
 *
 */

let { Ci, Cc } = require("chrome");
let Panel = require("panel").Panel;
let selection = require("selection");
const windowMediator = Cc["@mozilla.org/appshell/window-mediator;1"].
                       getService(Ci.nsIWindowMediator);

let node_ = null;

function context() {
  return windowMediator.getMostRecentWindow("navigator:browser").document.
         commandDispatcher.focusedWindow;
}

function trimStr(src) {
    return src.replace(/^[\0\s]+|[\0\s]+$/g,'');
}

exports.main = function() {
    let dictionaryPanel = new Panel({
        id: "dictionaryPanel",
        width: 405,
        height: 513,
        onHide: function() {
            node_.parentNode.removeChild(node_);
            node_ = null;
        }
    });

    let onSelection = function () {
        if (typeof(selection.text) == 'string') {
            var selected_text = trimStr(selection.text);
            if (selected_text.length > 0) {
                dictionaryPanel.contentURL = 'http://endic.naver.com/popManager.nhn?m=search&query=' + selected_text;
                let window_ = context();
                let selection_ = window_.getSelection();
                if (selection_.rangeCount < 1) {
                    return;
                }
                let curElement = window_.document.activeElement;
                if (curElement.nodeName.toLowerCase() == 'textarea'
                    || curElement.nodeName.toLowerCase() == 'input') {
                    return;
                }
                console.log(['\n'+prop+': '+selection_.anchorNode[prop] for (prop in selection_.anchorNode)].join(''));
                let range_ = selection_.getRangeAt(0);
                try {
                    if (node_ && node_.parentNode) {
                        node_.parentNode.removeChild(node_);
                    } else {
                        node_ = window_.document.createElement("span");
                    }
                } catch (e if e instanceof TypeError) {
                    node_ = window_.document.createElement("span");
                } finally {
                    range_.insertNode(node_);
                    dictionaryPanel.show(node_);
                }
            }
        }
    };

    selection.on('select', onSelection);
};