Parse a [youtube]videoID[/youtube] or [youtube]videoURL[/youtube] BBCode tag

youtube.js

var posts = document.getElementsByClassName("postmsg");
// don't allow videos in signatures

var j;

for (j = 0; j < posts.length; j++) {
var thishtml = posts[i].innerHTML;
var i;
var vids = [];
for (i = 0; i < thishtml.split("[youtube]").length-1; i++) {
  vids[i] = thishtml.split("[youtube]")[i+1].split("[/youtube]")[0];
  if (vids[i].indexOf("http://") != -1 || vids[i].indexOf("https://") != -1) {
    vids[i] = vids[i].split("v=")[1].split("&")[0];
    if (vids[i].indexOf("&") > vids[i].indexOf("v=")) {
      vids[i] = vids[i].split("&")[0];
    }
    vids[i] = decodeURIComponent(vids[i]);
  }
}

for (i = 0; i < vids.length; i++) {
  thishtml = thishtml.replace(/\[youtube\](.+?)\[\/youtube\]/i, "<iframe width=\"420\" height=\"315\" src=\"http://www.youtube.com/embed/"+vids[i]+"\" frameborder=\"0\" allowfullscreen></iframe>");
}


posts[i].innerHTML = thishtml;
}