Javascript ，事件处理程序总是被调用，即使事件没有被引发

2022-01-15 00:00:00 event-handling jquery javascript

我有以下代码扩展了 JQuery 并向 JQuery 添加了一个方法:

i have the following code which extends the JQuery and adds a method to the JQuery:

$.fn.attachWithMessage = function () {
  $(this).focusin(showMessage());
}

function showMessage() {
    alert('hi');
}

所以我可以按如下方式使用该代码:

so I can use that code as follows :

<input type="text" name="name" id="textbox" />
$(document).ready(function () {
   $("#textbox").attachWithMessage ();
});

当我第一次加载页面时，会出现一个带有 ('hi') 消息的消息框.

when I load the page for the first time, a message box shows up with ('hi') message.

即使我没有点击文本框.

even if I didn't click in the text box.

我也尝试了点击事件，消息仍然自动显示.

I also tried the click event, and the message still shows automatically.

有什么想法吗??

推荐答案

这里的问题是，当你将 showMessage() 作为参数传递给 focusin 时，函数showMessage 被执行，返回值被传递给focusin.

The issue here is that when you pass showMessage() as a parameter to focusin, the function showMessage is executed and the return value is passed to focusin.

相反，您需要传递对函数的引用(不带括号).

Instead you need to pass a reference to the function (without the paranthesis).

使用以下代码进行扩展:

Use the following code to extend:

$.fn.attachWithMessage = function () {   
  $(this).focusin(showMessage); 
}

工作示例@ http://jsfiddle.net/eXEP5/

如果您想将参数传递给 showMessage，请尝试以下操作:

If you want to pass a parameter to showMessage then try this:

$.fn.attachWithMessage = function () {   
  var param1 = "Some Param";
  $(this).focusin(function(){
     showMessage(param1); //Make sure showMessage is modified accordingly for the parameters.
  }); 
}

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