原生js实现ajax用于简单的签到或登录

<script>
function createStandardXHR() {
try {
return new window.XMLHttpRequest();
} catch( e ) {}
}
function createActiveXHR() {
try {
return new window.ActiveXObject( "Microsoft.XMLHTTP" );
} catch( e ) {}
}
function getXhr() {
var xhr = window.ActiveXObject !== undefined ?
// Support: IE6+
function() {
return createStandardXHR() || createActiveXHR();
} :
// For all other browsers, use the standard XMLHttpRequest object
createStandardXHR;
return xhr;
}
function get(url, callback){
var req = getXhr()();
if(req){
req.open("GET", url, true);
req.onreadystatechange = function(){
if(req.readyState == 4){
if(req.status == 200){
callback(req.responseText);
}else{
alert("error");
}
}
}
req.send(null);
}
}
!(function(win, document){
var ipt_email = document.getElementById('ipt_email');
ipt_email.onfocus = function(){
this.value = '';
};
var ipt_sub = document.getElementById('ipt_sub');
var tot_email = document.getElementById('tot_email');
ipt_sub.onclick = function(){
var val = ipt_email.value;
if(/\w/.test(val)){
var url = 'index.php?email_prefix=' + val;
get(url,function(data){
if ('1' === data) {
alert('签到成功！欢迎出席搜房十六周年庆典暨扩大管理会议！');
} else if ('2' === data) {
alert('对不起，您已经签到过！');
} else if ('3' === data) {
alert("对不起，还未到签到时间，请耐心等待！");
} else {
alert('对不起，未能匹配到您的信息，请核对邮箱！');
}
});
}else{
tot_email.getElementsByTagName('p')[0].innerHTML = '请正确输入邮箱地址！';
}
};
})(window, document)
</script>

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