Javascript 如何使用带有 jQuery 的 change() 方法的参数的函数？
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How to use a function that takes arguments with jQuery's change() method?
提问by Manos Dilaverakis
I'm using jQuery version 1.5. I am looking at jQuery's change()function and specifically at this bit:
我正在使用 jQuery 1.5 版。我正在查看 jQuery 的change()函数，特别是在这一点上：
.change( [ eventData ], handler(eventObject) )
eventData: A map of data that will be passed to the event handler.
handler(eventObject): A function to execute each time the event is triggered.
What exactly is a "map of data" in JavaScript? How can I use the following test function as an event handler?
JavaScript 中的“数据映射”究竟是什么？如何使用以下测试函数作为事件处理程序？
var myHandler = function(msg){alert(msg);};
I've tried this:
我试过这个：
$("select#test").change(["ok"], myHandler);
and the alert reports [object Object]
和警报报告 [object Object]
回答by Felix Kling
See event.data. The data is not passed as argument to handler, but as property of the event object:
见event.data。数据不是作为参数传递给处理程序，而是作为事件对象的属性：
$("select#test").change({msg: "ok"}, function(event) {
alert(event.data.msg);
});
The handler always only accepts one argument, which is the eventobject. This is the reason why your alert shows "[object Object]", your function is printing the event object.
If you want to use functions with custom arguments, you have to wrap them into another function:
处理程序始终只接受一个参数，即event对象。这就是为什么您的警报显示"[object Object]"，您的函数正在打印事件对象的原因。
如果要使用带有自定义参数的函数，则必须将它们包装到另一个函数中：
$("select#test").change({msg: "ok"}, function(event) {
myHandler(event.data.msg);
});
or just
要不就
$("select#test").change(function(event) {
myHandler("ok");
});
Btw. the selector is better written as $('#test'). IDs are (should be) unique. There is no need to prepend the tag name.
顺便提一句。选择器最好写成$('#test'). ID 是（应该）唯一的。无需预先添加标签名称。
回答by T.J. Crowder
What exactly is a "map of data" in Javascript?
Javascript 中的“数据映射”究竟是什么？
Basically just an object, e.g.:
基本上只是一个对象，例如：
var data = {
foo: "I'm foo",
bar: "I'm bar"
};
All JavaScript objects are essentially maps (aka "dictionaries" aka "associative arrays").
所有 JavaScript 对象本质上都是映射（又名“字典”又名“关联数组”）。
How can I use the following test function as an event handler?
如何使用以下测试函数作为事件处理程序？
By wrapping it in another function:
通过将其包装在另一个函数中：
$("select#test").change(function() {
myHandler($(this).val());
});
That calls myHandlerwith the value of the select box whenever it changes.
myHandler每当它改变时，就会调用选择框的值。
If you want to use the eventDatapart, add an object prior to the handler:
如果要使用该eventData部件，请在处理程序之前添加一个对象：
$("select#test").change({
foo: "I'm foo"
}, function(event) {
myHandler(event.data.foo, $(this).val());
});
That calls myHandlerwith the "I'm foo" as the first argument, then the value of the select box, whenever it changes.
调用myHandler时将“I'm foo”作为第一个参数，然后是选择框的值，只要它发生变化。
