为什么当我的页面加载而不是单击我的单选按钮时触发我的 onchange 事件？

Question

I have the following code in my Javascript. I'd like the alert to happen when a user checks the radio button, but instead it happens when the page loads, and NOTHING happens when the radio button gets checked. Why?

var myRadioButton = document.getElementById("myRadioButton");
myRadioButton.onchange=alert("Checked!");

The radio button starts off unchecked. In the HTML it looks like this:

<div class="myRadioButton"><input type="radio" id="myRadioButton" name="radioButtons"  />&nbsp; This is my radio button 
</div>

Why on earth would the Javascript think an onchange event has occurred when the page loads? And why doesn't it recognize a change when I actually check the radio button?

In fact, whatever element I use with onchange makes the alert pop up when the page loads, without any user interaction at all. Am I misunderstanding how onchange works?

Answer 1

What you mean to do is

myradiobutton.onchange = function() { alert('Checked'); };

What you did will execute the alert -function and assign the return value of that function as an event handler to the onchange event (which will do nothing when executed)

Answer 2

try

<script>
    var myRadioButton = document.getElementById("myRadioButton");

    myRadioButton.onchange = function () { alert("Checked!") };
</script>

Answer 3

In your code

myradiobutton.onchange = alert('Checked')

You actually called alert function, and assigned its return value as event handler.