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我是一個嘗試處理JavaScript的Perl編碼器。嘗試創建AJAX請求但功能始終返回undefined
。這段代碼有什麼問題?如何讓它正常工作?Javascript函數返回undefined而不是對象
var url = 'http://local.com/cgi-bin/hello2.pl';
var params = 'a=b&c=d';
// url returns a plain text:
// 1234567890 2013 05 May Friday 13 23 45 01
var enddate = getEndDate(url, params);
var dow = enddate.EDDAYOW; // must be a 'Friday' but returns undefined
alert(dow);
function getEndDate(url, params) {
var myRequest = new ajaxObject(url);
myRequest.callback = function(responseText) {
if (responseText.length > 20) {
var n = responseText.split(" ");
return {
'edseconds': n[0],
'EDYEAR': n[1],
'EDMON': n[2],
'EDMONNAME': n[3],
'EDDAYOW': n[4],
'EDDAY': n[5],
'EDHOUR': n[6],
'EDMIN': n[7],
'EDSEC': n[8]
};
} else {
getEndDate(url, params);
}
}
myRequest.update(params);
}
function ajaxObject(url, callbackFunction) {
var that = this;
this.updating = false;
this.abort = function() {
if (that.updating) {
that.updating = false;
that.AJAX.abort();
that.AJAX = null;
}
}
this.update = function(passData, postMethod) {
if (that.updating) {
return false;
}
that.AJAX = null;
if (window.XMLHttpRequest) {
that.AJAX = new XMLHttpRequest();
} else {
that.AJAX = new ActiveXObject("Microsoft.XMLHTTP");
}
if (that.AJAX == null) {
return false;
} else {
that.AJAX.onreadystatechange = function() {
if (that.AJAX.readyState == 4) {
that.updating = false;
that.callback(that.AJAX.responseText, that.AJAX.status, that.AJAX.responseXML);
that.AJAX = null;
}
}
that.updating = new Date();
if (/post/i.test(postMethod)) {
var uri = urlCall + '?' + that.updating.getTime();
that.AJAX.open("POST", uri, true);
that.AJAX.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
that.AJAX.setRequestHeader("Content-Length", passData.length);
that.AJAX.send(passData);
} else {
var uri = urlCall + '?' + passData + '&timestamp=' + (that.updating.getTime());
that.AJAX.open("GET", uri, true);
that.AJAX.send(null);
}
return true;
}
}
var urlCall = url;
this.callback = callbackFunction ||
function() {};
}
歡迎來到** async **的美妙世界!你不能那樣做。 – SLaks 2013-05-12 21:13:44
Ajax請求是異步的,而javascript作爲一個整體主要是事件驅動的。您將要更改代碼的結構,可能會向'getEndDate'函數添加回調。瑣事,Ajax中的** A **實際上代表異步。 – 2013-05-12 21:18:26
您的'getEndDate()'沒有'return'語句,所以它隱含地返回'undefined'。 (你編寫的'return'語句在回調的匿名函數中,所以它從_that_函數返回並被忽略,它不會從'getEndDate()'返回。) – nnnnnn 2013-05-12 21:20:29