実行するとモニターの真ん中にtwitterのwindowを出す関数
function tweetPop() {
var url = "https://twitter.com/share?";
url += "text=" + encodeURI("example_text");
url += "&via=twitter_account";
url += "&url=" + encodeURI("http://example.com/");
url += "&hashtags=" + encodeURI("hashtag");
var popW = 550;
var popH = 420;
var x = (screen.width - popW) / 2;
var y = (screen.height - popH) / 2;
var size = 'width=' + popW;
size += ',height=' + popH;
size += ',top=' + y;
size += ',left=' + x;
window.open(url, "tweetPop", size);
}