javascript 取消下拉列表更改事件时如何设置以前的值
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How to set previous value when cancelling a drop-down list change event
提问by Royal Pinto
I am designing a html page. I want to show a confirmation msg on changing a drop down element using jquery or javascript. Please help to do this.
我正在设计一个 html 页面。我想在使用 jquery 或 javascript 更改下拉元素时显示确认消息。请帮助做到这一点。
I have code which will ask confirmation. On selecting cancel it will not select previous item of Drop down.
我有要求确认的代码。在选择取消时，它不会选择下拉的上一项。
$("#dropdownId").change(function(e)
{
if($(this).val() == "40")
{
if(confirm("Are you sure"))
return true;
else
return false;
}
});
Thanks
谢谢
回答by Can Gencer
You should be able to store the previous value on the click event and set it back on the change event:
您应该能够在 click 事件上存储先前的值并将其重新设置在 change 事件上：
var setLastSelected = function(element) {
$(element).data('lastSelected', $(element).find("option:selected"));
};
$("select").each(function () {
setLastSelected(this);
});
$("select").change(function(){
if(confirm("Are you sure")) {
setLastSelected(this);
return true;
}
else {
$(this).data('lastSelected').attr("selected", true);
return false;
}
});
See: http://jsfiddle.net/w9JYX/14/
见：http: //jsfiddle.net/w9JYX/14/
Update: I updated the code to work more generically on a set of dropdown controls and also removed the click handler.
更新：我更新了代码以在一组下拉控件上更通用地工作，并删除了点击处理程序。
回答by Shef
var previous_option = $('#dropdownId option:selected');
$("#dropdownId").change(function(e){
var $this = $(this),
selected = $this.find('option:selected');
if($this.val() == "40"){
if(confirm("Are you sure")){
previous_option = selected;
return true;
} else{
selected.removeAttr('selected');
previous_option.attr('selected', 'selected');
}
} else{
previous_option = selected;
}
});
回答by DShook
Here's a bit tighter solution along the same lines without having to create global variables or other functions:
这里有一个更严格的解决方案，无需创建全局变量或其他函数：
$('#dropdownId')
.on('focus', function () {
$(this).data("prev", $(this).val());
})
.change(function () {
if (confirm('Are you sure?')) {
//normal case where the dropdown changes
$(this).data("prev", $(this).val());
} else {
//if the user doesn't confirm reset the dropdown back to what it was
$(this).val($(this).data("prev"));
}
});
回答by RFE Petr
Usage for ASP.NET page:
ASP.NET 页面的用法：
$("#<%= dropdownId.ClientID %>")
.on('focus', function () {
$(this).data("prev", $(this).val());
})
.change(function () {
if (confirm('Are you sure?')) {
$(this).data("prev", $(this).val());
} else {
$(this).val($(this).data("prev"));
}
});
