quick xhr post example

xhr-post.js

// USAGE
//    post('http://example.com', {name:'brian'}, console.log)
var post = function(url, params, cb) {
   var x = new XMLHttpRequest()
   ,   p = ''

   x.onreadystatechange = function() {
       if (x.readyState === 4)
         cb.call(this, x.status)
   }

   for (var i in params)
       p += i +'='+ params[i] +'&'

   x.open("POST", url, true)
   x.setRequestHeader("Content-type", "application/x-www-form-urlencoded")
   x.send(p.substring(0, params.length-1))
}

I know this is an OLD gist, but there is a typo. The line:
x.send(p.substring(0, params.length-1))

should be:
x.send(p.substring(0, p.length-1))

Hope that helps anyone who runs across this!