开发者

javascript value is null

开发者 https://www.devze.com 2023-03-25 15:17 出处:网络
Ok so here it goes im totally lost a bit and im a beg开发者_运维问答inner. A friend of mine has a radio website, it a really old site.

Ok so here it goes im totally lost a bit and im a beg开发者_运维问答inner.

A friend of mine has a radio website, it a really old site.

Has a form where he can uptade the users.

This form has a radio button named dj and values yes or no.

and on the index page it shows the list of the users.

and i would like to do if this radio button is checked, than add a small dj image after the users name.

but no matter what i do im always getting the value null.

the header and footer are included in both of the files, if im right that suppose to give the result no? i placed in the footer its giving back nulll as result

var dj = document.getElementById("dj");
alert(dj.value);

i tried wit the wondow.onload function nothing happens.

I would really like to do this in javascript for practis.

Could somebody please explain what im missing and why i cant get this to show on the index? and is it possible ot make it?

Be gentlle please im a really big beginner :)


Try

 alert(dj.checked);

It will alert true or false depending upon the status of radio button if you created your radio button smiler to this

<input type="radio" name="music" value="test" id="dj">


I've created a working example (though not elegant) which illustrates exactly what needs to be done since you've mentioned you're a beginner.

http://sente.cc/misc/radio_button_test.html

The code is:

 <html>
   <head>
     <meta http-equiv="content-type" content="text/html; charset=utf-8">
     <title>radio buttons</title>
     <script>
       var testit = function(){
         var radioyes = document.getElementById('idyes');
         var radiono = document.getElementById('idno');

         if (radioyes.checked){alert(radioyes.value);}
         if (radiono.checked){alert(radiono.value);}
       };
     </script>
   </head>
   <body>
     <form>
       DJ:
       <br>
       <input id="idyes" type="radio" name="sex" value="yes" /> Yes<br />
       <input id="idno"  type="radio" name="sex" value="no" /> No
     </form>
   </body>
   <span style="background:lightblue;" onclick="javascript:testit()">click here to run javascript</span>
 </html>

There are much better ways of going about this. (like iterating through all the radio elements until you come across one with a .checked property of true)


Probably both radio buttons have the same ID, so such code can't work.

Instead, try this: (assuming you have only one form)

var oForm = document.forms[0];
var value = "";
for (var i = 0; i < oForm.elements.length; i++) {
    var el = oForm.elements[i];
    if (el.type == "radio" && el.name == "dj" && el.checked) {
        value = el.value;
        break;
    }
}
alert("selected value: " + value);

The code is pretty much straightforward.

Live test case.


I would reference the jQuery library and use this code:

$(document).ready(function() {
  alert($("#dj").val());
});
0

精彩评论

暂无评论...
验证码 换一张
取 消