然后这是错误，var的值不会改变。我做错了什么？ stackoverflow的更多细节！ stackoverflow的更多细节！有关stackoverflow的更多详细信息！
function set(id, edate)
{
var good = true;
$.post("ajax.php", { func: "set", id: id, edate: edate},
function(data){
data = JSON.parse(data);
if(data.error) {
good = false;
if(data.emessage=='SqlError') { alert('Ошибка выполнения запроса, перезагрузите страницу и попробуйте снова.'); }
}
else {
if(data.emessage=='AddOk') { alert('Запись о выданной зарплате успешно создана!'); }
else if(data.emessage=='DeleteOk') { alert('Выдача зарплаты ОТМЕНЕНА успешно!'); }
}
}
);
return good;
}
答案 0 :(得分：0)
问题是你有一个异步函数（AJAX POST）来操纵你的变量。 您无法直接返回变量，而是考虑使用以下内容：
function set(id, edate, callback)
{
$.post("ajax.php", { func: "set", id: id, edate: edate},
function(data){
data = JSON.parse(data);
if(data.error) {
callback(false);
}else{
callback(true);
}
}
);
}
用法：
set(id, edate, function(good){
});
$.post异步？ $.post的Jquery来源：
function (url, data, callback, type) {
// Shift arguments if data argument was omitted
if (jQuery.isFunction(data)) {
type = type || callback;
callback = data;
data = undefined;
}
// The url can be an options object (which then must have .url)
return jQuery.ajax(jQuery.extend({
url: url,
type: method,
dataType: type,
data: data,
success: callback
},
jQuery.isPlainObject(url) && url));
}
调用JQuery.ajax：
function (url, options) {
// If url is an object, simulate pre-1.5 signature
if (typeof url === "object") {
options = url;
url = undefined;
}
// Force options to be an object
options = options || {};
var transport,
// URL without anti-cache param
cacheURL,
// Response headers
responseHeadersString, responseHeaders,
// timeout handle
timeoutTimer,
// Url cleanup var
urlAnchor,
// To know if global events are to be dispatched
fireGlobals,
// Loop variable
i,
// Create the final options object
s = jQuery.ajaxSetup({},
options),
// Callbacks context
callbackContext = s.context || s,
// Context for global events is callbackContext if it is a DOM node or jQuery collection
globalEventContext = s.context && (callbackContext.nodeType || callbackContext.jquery) ? jQuery(callbackContext) : jQuery.event,
// Deferreds
deferred = jQuery.Deferred(),
completeDeferred = jQuery.Callbacks("once memory"),
// Status-dependent callbacks
statusCode = s.statusCode || {},
// Headers (they are sent all at once)
requestHeaders = {},
requestHeadersNames = {},
// The jqXHR state
state = 0,
// Default abort message
strAbort = "canceled",
// Fake xhr
jqXHR = {
readyState: 0,
// Builds headers hashtable if needed
getResponseHeader: function (key) {
var match;
if (state === 2) {
if (!responseHeaders) {
responseHeaders = {};
while ((match = rheaders.exec(responseHeadersString))) {
responseHeaders[match[1].toLowerCase()] = match[2];
}
}
match = responseHeaders[key.toLowerCase()];
}
return match == null ? null : match;
},
// Raw string
getAllResponseHeaders: function () {
return state === 2 ? responseHeadersString : null;
},
// Caches the header
setRequestHeader: function (name, value) {
var lname = name.toLowerCase();
if (!state) {
name = requestHeadersNames[lname] = requestHeadersNames[lname] || name;
requestHeaders[name] = value;
}
return this;
},
// Overrides response content-type header
overrideMimeType: function (type) {
if (!state) {
s.mimeType = type;
}
return this;
},
// Status-dependent callbacks
statusCode: function (map) {
var code;
if (map) {
if (state < 2) {
for (code in map) {
// Lazy-add the new callback in a way that preserves old ones
statusCode[code] = [statusCode[code], map[code]];
}
} else {
// Execute the appropriate callbacks
jqXHR.always(map[jqXHR.status]);
}
}
return this;
},
// Cancel the request
abort: function (statusText) {
var finalText = statusText || strAbort;
if (transport) {
transport.abort(finalText);
}
done(0, finalText);
return this;
}
};
// Attach deferreds
deferred.promise(jqXHR);
// Remove hash character (#7531: and string promotion)
// Add protocol if not provided (prefilters might expect it)
// Handle falsy url in the settings object (#10093: consistency with old signature)
// We also use the url parameter if available
s.url = ((url || s.url || location.href) + "").replace(rhash, "").replace(rprotocol, location.protocol + "//");
// Alias method option to type as per ticket #12004
s.type = options.method || options.type || s.method || s.type;
// Extract dataTypes list
s.dataTypes = jQuery.trim(s.dataType || "*").toLowerCase().match(rnotwhite) || [""];
// A cross-domain request is in order when the origin doesn't match the current origin.
if (s.crossDomain == null) {
urlAnchor = document.createElement("a");
// Support: IE8-11+
// IE throws exception if url is malformed, e.g. http://example.com:80x/
try {
urlAnchor.href = s.url;
// Support: IE8-11+
// Anchor's host property isn't correctly set when s.url is relative
urlAnchor.href = urlAnchor.href;
s.crossDomain = originAnchor.protocol + "//" + originAnchor.host !== urlAnchor.protocol + "//" + urlAnchor.host;
} catch(e) {
// If there is an error parsing the URL, assume it is crossDomain,
// it can be rejected by the transport if it is invalid
s.crossDomain = true;
}
}
// Convert data if not already a string
if (s.data && s.processData && typeof s.data !== "string") {
s.data = jQuery.param(s.data, s.traditional);
}
// Apply prefilters
inspectPrefiltersOrTransports(prefilters, s, options, jqXHR);
// If request was aborted inside a prefilter, stop there
if (state === 2) {
return jqXHR;
}
// We can fire global events as of now if asked to
// Don't fire events if jQuery.event is undefined in an AMD-usage scenario (#15118)
fireGlobals = jQuery.event && s.global;
// Watch for a new set of requests
if (fireGlobals && jQuery.active++===0) {
jQuery.event.trigger("ajaxStart");
}
// Uppercase the type
s.type = s.type.toUpperCase();
// Determine if request has content
s.hasContent = !rnoContent.test(s.type);
// Save the URL in case we're toying with the If-Modified-Since
// and/or If-None-Match header later on
cacheURL = s.url;
// More options handling for requests with no content
if (!s.hasContent) {
// If data is available, append data to url
if (s.data) {
cacheURL = (s.url += (rquery.test(cacheURL) ? "&" : "?") + s.data);
// #9682: remove data so that it's not used in an eventual retry
delete s.data;
}
// Add anti-cache in url if needed
if (s.cache === false) {
s.url = rts.test(cacheURL) ?
// If there is already a '_' parameter, set its value
cacheURL.replace(rts, "$1_=" + nonce++) :
// Otherwise add one to the end
cacheURL + (rquery.test(cacheURL) ? "&" : "?") + "_=" + nonce++;
}
}
// Set the If-Modified-Since and/or If-None-Match header, if in ifModified mode.
if (s.ifModified) {
if (jQuery.lastModified[cacheURL]) {
jqXHR.setRequestHeader("If-Modified-Since", jQuery.lastModified[cacheURL]);
}
if (jQuery.etag[cacheURL]) {
jqXHR.setRequestHeader("If-None-Match", jQuery.etag[cacheURL]);
}
}
// Set the correct header, if data is being sent
if (s.data && s.hasContent && s.contentType !== false || options.contentType) {
jqXHR.setRequestHeader("Content-Type", s.contentType);
}
// Set the Accepts header for the server, depending on the dataType
jqXHR.setRequestHeader("Accept", s.dataTypes[0] && s.accepts[s.dataTypes[0]] ? s.accepts[s.dataTypes[0]] + (s.dataTypes[0] !== "*" ? ", " + allTypes + "; q=0.01" : "") : s.accepts["*"]);
// Check for headers option
for (i in s.headers) {
jqXHR.setRequestHeader(i, s.headers[i]);
}
// Allow custom headers/mimetypes and early abort
if (s.beforeSend && (s.beforeSend.call(callbackContext, jqXHR, s) === false || state === 2)) {
// Abort if not done already and return
return jqXHR.abort();
}
// Aborting is no longer a cancellation
strAbort = "abort";
// Install callbacks on deferreds
completeDeferred.add(s.complete);
jqXHR.done(s.success);
jqXHR.fail(s.error);
// Get transport
transport = inspectPrefiltersOrTransports(transports, s, options, jqXHR);
// If no transport, we auto-abort
if (!transport) {
done(-1, "No Transport");
} else {
jqXHR.readyState = 1;
// Send global event
if (fireGlobals) {
globalEventContext.trigger("ajaxSend", [jqXHR, s]);
}
// If request was aborted inside ajaxSend, stop there
if (state === 2) {
return jqXHR;
}
// Timeout
if (s.async && s.timeout > 0) {
timeoutTimer = window.setTimeout(function () {
jqXHR.abort("timeout");
},
s.timeout);
}
try {
state = 1;
transport.send(requestHeaders, done);
} catch(e) {
// Propagate exception as error if not done
if (state < 2) {
done(-1, e);
// Simply rethrow otherwise
} else {
throw e;
}
}
}
// Callback for when everything is done
function done(status, nativeStatusText, responses, headers) {
var isSuccess, success, error, response, modified, statusText = nativeStatusText;
// Called once
if (state === 2) {
return;
}
// State is "done" now
state = 2;
// Clear timeout if it exists
if (timeoutTimer) {
window.clearTimeout(timeoutTimer);
}
// Dereference transport for early garbage collection
// (no matter how long the jqXHR object will be used)
transport = undefined;
// Cache response headers
responseHeadersString = headers || "";
// Set readyState
jqXHR.readyState = status > 0 ? 4 : 0;
// Determine if successful
isSuccess = status >= 200 && status < 300 || status === 304;
// Get response data
if (responses) {
response = ajaxHandleResponses(s, jqXHR, responses);
}
// Convert no matter what (that way responseXXX fields are always set)
response = ajaxConvert(s, response, jqXHR, isSuccess);
// If successful, handle type chaining
if (isSuccess) {
// Set the If-Modified-Since and/or If-None-Match header, if in ifModified mode.
if (s.ifModified) {
modified = jqXHR.getResponseHeader("Last-Modified");
if (modified) {
jQuery.lastModified[cacheURL] = modified;
}
modified = jqXHR.getResponseHeader("etag");
if (modified) {
jQuery.etag[cacheURL] = modified;
}
}
// if no content
if (status === 204 || s.type === "HEAD") {
statusText = "nocontent";
// if not modified
} else if (status === 304) {
statusText = "notmodified";
// If we have data, let's convert it
} else {
statusText = response.state;
success = response.data;
error = response.error;
isSuccess = !error;
}
} else {
// Extract error from statusText and normalize for non-aborts
error = statusText;
if (status || !statusText) {
statusText = "error";
if (status < 0) {
status = 0;
}
}
}
// Set data for the fake xhr object
jqXHR.status = status;
jqXHR.statusText = (nativeStatusText || statusText) + "";
// Success/Error
if (isSuccess) {
deferred.resolveWith(callbackContext, [success, statusText, jqXHR]);
} else {
deferred.rejectWith(callbackContext, [jqXHR, statusText, error]);
}
// Status-dependent callbacks
jqXHR.statusCode(statusCode);
statusCode = undefined;
if (fireGlobals) {
globalEventContext.trigger(isSuccess ? "ajaxSuccess" : "ajaxError", [jqXHR, s, isSuccess ? success : error]);
}
// Complete
completeDeferred.fireWith(callbackContext, [jqXHR, statusText]);
if (fireGlobals) {
globalEventContext.trigger("ajaxComplete", [jqXHR, s]);
// Handle the global AJAX counter
if (! (--jQuery.active)) {
jQuery.event.trigger("ajaxStop");
}
}
}
return jqXHR;
}
Jquery事件：
$.fn.ajaxStart = function ( handler ) { return this.on('ajaxStart', handler); };
$.fn.ajaxStop = function ( handler ) { return this.on('ajaxStop', handler); };
$.fn.ajaxComplete = function ( handler ) { return this.on('ajaxComplete', handler); };
$.fn.ajaxError = function ( handler ) { return this.on('ajaxError', handler); };
$.fn.ajaxSuccess = function ( handler ) { return this.on('ajaxSuccess', handler); };
$.fn.ajaxSend = function ( handler ) { return this.on('ajaxSend', handler); };
jQuery.ajaxSetup：
function (target, settings) {
return settings ?
// Building a settings object
ajaxExtend(ajaxExtend(target, jQuery.ajaxSettings), settings) :
// Extending ajaxSettings
ajaxExtend(jQuery.ajaxSettings, target);
}
jQuery.ajax设置：
{
"url": "http://james.padolsey.com/jquery/#v=git&fn=",
"type": "GET",
"isLocal": false,
"global": true,
"processData": true,
"async": true,
"contentType": "application/x-www-form-urlencoded; charset=UTF-8",
"accepts": {
"*": "*/*",
"text": "text/plain",
"html": "text/html",
"xml": "application/xml, text/xml",
"json": "application/json, text/javascript",
"script": "text/javascript, application/javascript, application/ecmascript, application/x-ecmascript"
},
"contents": {
"xml": {},
"html": {},
"json": {},
"script": {}
},
"responseFields": {
"xml": "responseXML",
"text": "responseText",
"json": "responseJSON"
},
"converters": {
"text html": true
},
"flatOptions": {
"url": true,
"context": true
},
"jsonp": "callback"
}
XHR：
jQuery.ajaxSettings.xhr = window.ActiveXObject !== undefined ?
// Support: IE6+
function() {
// XHR cannot access local files, always use ActiveX for that case
return !this.isLocal &&
// Support: IE7-8
// oldIE XHR does not support non-RFC2616 methods (#13240)
// See http://msdn.microsoft.com/en-us/library/ie/ms536648(v=vs.85).aspx
// and http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9
// Although this check for six methods instead of eight
// since IE also does not support "trace" and "connect"
/^(get|post|head|put|delete|options)$/i.test( this.type ) &&
createStandardXHR() || createActiveXHR();
} :
// For all other browsers, use the standard XMLHttpRequest object
createStandardXHR;
var xhrId = 0,
xhrCallbacks = {},
xhrSupported = jQuery.ajaxSettings.xhr();
// Support: IE<10
// Open requests must be manually aborted on unload (#5280)
// See https://support.microsoft.com/kb/2856746 for more info
if ( window.attachEvent ) {
window.attachEvent( "onunload", function() {
for ( var key in xhrCallbacks ) {
xhrCallbacks[ key ]( undefined, true );
}
});
}
最终jQuery.ajaxSettings.xhr决定了为与服务器通信创建的对象类型。
所有现代浏览器都支持XMLHttpRequest对象（IE5和IE6使用 一个ActiveXObject）。
XMLHttpRequest对象用于与服务器交换数据 在幕后。这意味着可以更新a的部分 网页，无需重新加载整个页面。
＆＃34;如果您使用扩展程序中的XMLHttpRequest，则应使用它 异步。在这种情况下，您会在数据时收到回调 已收到，这使浏览器继续正常工作 正在处理您的请求。＆＃34;
您可以使XMLHttpRequest同步，JQUERY允许您这样做（ reffer to jquery.ajax.settings [＆＃34; asyc＆＃34;] ）;但是，默认情况下启用asyc。