Nano.js. A 25-line jQuery impersonator. Complete Version

nano.js

var $ = function(s){ // Makes the main function (accepts one value)
  var o = []// Makes an empty array
  var sel = s.substring(1,s.length) // Get's the selector text minus the first character (like #)
  switch (s.charAt(0)){ // Switch based on first chararcter
  case '#': // If it's a #, do document.getElementById
    o.push(document.getElementById(sel))// the element is pushed to o instead of the element being returned
   break; 
  case '.': // If it's a ., get the element by class name
     o.push(document.getElementsByClassName(sel))
    break; 
  case '*': // If a star, do document.getElementByTagName
    o.push(document.getElementsByTagName(sel)) 
    break; 
} 
for (var i in o){ //Gives all the nodes inside o the on method
     o[i].on = function(type, callback)
   {this.addEventListener(type, callback);return this}
  }
  if (o.length === 1){ // If o only has 1 element
  return o[0] // Returns the element
  }
      else {
   return o // Returns element list
  }
  }