DOM building like MochiKit

tag.js

function append(elem, value) {
  if (typeof value == 'string') {
    elem.innerHTML = value.replace(/\r\n/g, "\n").replace(/\n/g, '<br />')
  } else if (typeof value == 'undefined') {
  } else if (value.constructor == Array) {
    for (var v in value) {arguments.callee(elem, value[v])}
  } else {
    elem.appendChild(value)
  }
  return elem
}

function tag(name, opts, value) {
  var opts = opts || {}
  var elem = document.createElement(name)
  for (key in opts) {
    if (key == 'class') {
      elem['className'] = opts[key]
    } else {
      elem[key] = opts[key]
    }
  }
  return append(elem, value)
}
var tags = ['div','span','a','h1','h2','h3','p','br','form','label','input','textarea']
for (var t in tags) {
  eval("function "+tags[t]+"(opts, value){return tag('"+tags[t]+"', opts, value)}")
}