在任何 AJAX 调用之前触发 javascript 函数
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trigger a javascript function before on any AJAX call
提问by Vikrant
Here, I have a function which needs to be called before any AJAX call present in the .NET project.
在这里，我有一个函数需要在 .NET 项目中存在的任何 AJAX 调用之前调用。
Currently, I have to call checkConnectionon every button click which is going to invoke AJAX method, if net connection is there, proceeds to actual AJAXcall!
Anyhow, I want to avoid this way and the checkConnectionfunction should be called automatically before any AJAX call on the form.
目前，我必须调用checkConnection将调用 AJAX 方法的每个按钮单击，如果存在网络连接，则继续进行实际的AJAX调用！
无论如何，我想避免这种方式，并且checkConnection应该在表单上的任何 AJAX 调用之前自动调用该函数。
In short, I want to make function behave like an eventwhich will be triggered before any AJAX call
简而言之，我想让函数表现得像event在任何 AJAX 调用之前触发的
Adding sample, which makes AJAX call on button click; Of course, after checking internet availability...
添加示例，在单击按钮时进行 AJAX 调用；当然，在检查互联网可用性之后......
//check internet availability
function checkConnection() {
//stuff here to check internet then, set return value in the variable
return Retval;
}
//Ajax call
function SaveData() {
var YearData = {
"holiday_date": D.getElementById('txtYears').value
};
$.ajax({
type: "POST",
url: 'Service1.svc/SaveYears',
data: JSON.stringify(YearData),
contentType: "application/json; charset=utf-8",
dataType: "json",
processData: true,
success: function (data, status, jqXHR) {
//fill page data from DB
},
error: function (xhr) {
alert(xhr.responseText);
}
});
}
And below is current way to call function:
以下是当前调用函数的方式：
<form onsubmit="return Save();">
<input type="text" id="txtYears" /><br />
<input type="submit" id="btnSave" onclick="return checkConnection();" value="Save" />
<script>
function Save() {
if (confirm('Are you sure?')) {
SaveData();
}
else {
return false;
}
}
</script>
</form>
回答by Brijesh Bhatt
You cannot implicitly call a function without actually writing a call even once(!) in JavaScript.
在 JavaScript 中，您不能在没有实际编写调用的情况下隐式调用函数（！）。
So, better to call it in actual AJAXand for that you can use beforeSendproperty of ajaxRequest like following, hence there will be no need to call checkConnection()seperately:
因此，最好在实际中调用它，AJAX为此您可以使用beforeSendajaxRequest 的属性，如下所示，因此无需checkConnection()单独调用：
$.ajax({
type: "POST",
url: 'Service1.svc/SaveYears',
data: JSON.stringify(YearData),
contentType: "application/json; charset=utf-8",
dataType: "json",
processData: true,
beforeSend: function() {
if(!checkConnection())
return false;
},
success: function (data, status, jqXHR) {
//fill page data from DB
},
error: function (xhr) {
alert(xhr.responseText);
}
});
It reduces the call that you have made onsubmit()of formtag!
它减少了您onsubmit()对form标签的调用！
UPDATE: to register a global function before every AJAX request use:
更新：在每个 AJAX 请求使用之前注册一个全局函数：
$(document).ajaxSend(function() {
if(!checkConnection())
return false;
});
回答by Nikos M.
The best way is to use a publish-subsribe pattern to add any extra functions to be called on pre-determined times (either before or after ajax for example).
最好的方法是使用发布订阅模式来添加任何额外的函数，以便在预定的时间（例如在 ajax 之前或之后）调用。
jQuery already supports custom publish-subsrcibe
jQuery 已经支持自定义发布订阅
For this specific example just do this:
对于此特定示例，只需执行以下操作：
//Ajax call
function SaveData(element) {
var doAjax = true;
var YearData = {
"holiday_date": D.getElementById('txtYears').value
};
if (element === myForm)
{
doAjax = checkConnection();
}
if ( doAjax )
{
$.ajax({
type: "POST",
url: 'Service1.svc/SaveYears',
data: JSON.stringify(YearData),
contentType: "application/json; charset=utf-8",
dataType: "json",
processData: true,
success: function (data, status, jqXHR) {
//fill page data from DB
},
error: function (xhr) {
alert(xhr.responseText);
}
});
}
else
{
// display a message
}
}
Hope i understand correctly what you mean.
希望我能正确理解你的意思。
UPDATE:
更新：
in the ifyou can do an additional check if the function is called from the form or a field (for example add an argument SaveData(element))
在if你可以做一个额外的检查，如果函数是从表单或字段调用的（例如添加一个参数 SaveData(element)）
If you use the saveData in html, do this: "saveData(this)", maybe you should post your html as well
如果您在 html 中使用 saveData，请执行以下操作："saveData(this)"，也许您也应该发布您的 html
回答by Tell Me How
You can use:
您可以使用：
$(document)
.ajaxStart(function () {
alert("ajax start");
})
.ajaxComplete(function () {
alert("ajax complete");
})
That's it!!
而已！！
回答by ozil
use
利用
beforeSend: function () {
},
ajaxmethod
ajax方法
