js全局变量在其他方法中赋值后无法影响到该方法外的全局变量的值（奇葩问题）

$(document).ready(function(){
var strCookie=document.cookie;
username="1";
if (strCookie) {
cookieVariables = strCookie.split(";");
for (i = 0; i < cookieVariables.length; i++) {
cookieName = cookieVariables[i].split("=");
if (cookieName[0] === "username"){
username=cookieName[1];
alert(cookieName[1]);
}
}
}
alert(username);
});

$(document).ready(function(){
var strCookie=document.cookie;
username=getname(username);
function getname(username){
if (strCookie) {
cookieVariables = strCookie.split(";");
for (i = 0; i < cookieVariables.length; i++) {
cookieName = cookieVariables[i].split("=");
if (cookieName[0] === username){
return cookieName[1];
alert("cookieName[1]");
}
}
}else{
return "1";
}
}
alert(username);
});