I have an open source fla that reads a xml for an array and I ran across this code. Can any of you gurus tell me what this means?

multiNodeObject.prototype.length = function() {
var count = 0;
for (var name in this) {
var addCount = true;
for (var i = 0; i<name.length; i++) {
if (name.charCodeAt(i)<48 || name.charCodeAt(i)>57) {
addCount = false;
}
}
if (addCount) {
count++;
}
}
return count;
};

Specifically the charCodeAt code -- I'm lost, thanks!