如何验证单选按钮？

Question

How i put validation on check box?

Here is my code:

<script>
function Validate(){
   var cntct = document.getElementById("contact").value;
   if (cntct.value=="")
   {
      alert("Please select contact medium");
      return false;
   }
}
</script>

<input type="radio" name="contact" id="contact" value="SMS">
<label>SMS</label> <input type="radio" name="contact" id="contact" value="CALL">
<label>CALL</label> <input type="radio" name="contact" id="contact" value="EMAIL">
<label>EMAIL</label>

please help..

Answer 1

Simple: if(cntct == "") {

}

The cntct variable is the value!

Answer 2

in case of checkboxes and radiobuttons, the element is checked when the "checked" property is true:

function Validate(){
    var selectedValue = "";
    var cntct = document.getElementsByname("contact");
    for(var i=0;i<cntct.length;i++) {
        if (cntct[i].checked)
        {
            selectedValue = cntct.value;
        }
    }
    if(selectedValue == "") {
        alert("Please select contact medium");
        return false;
    }
    return true;
}

UPDATE

I just noticed that you have multiple elements with the same ID. This is not allowed, in such case the browser will return only the last element with that ID. You need to iterate over the elements with the same name and pick one with attribute checked . See the code above

Answer 3

How i put validation on check box?

I presume you mean "how do I make sure one of the radio buttons is checked when the form is submitted" (supposing there is a form you haven't shown).

The simple way is to make one checkbox selected by default, then you know that one will always be selected and you don't have to check, eg

<input type="radio" name="contact" value="CALL" checked>
<input type="radio" name="contact" value="EMAIL">

The other way is to loop over the radio buttons when the form is submitted (or whatever event you decide to base the validation on) and make sure one is checked. eg

function checkButton() {
  var nodes = document.getElementsByName('contact');
  for (var i=0, iLen=nodes.length; i<iLen; i++) {

    // If find a checked one, job's done
    if (nodes[i].checked) return true;
  }

  // Otherwise, none were checked
  return false;
}

There is an input type text with a name of contact, but it won't have a checked property so will be treated like an unchecked radio.

Answer 4

Please try this:

<script>
function SubmitIt()
{
    if (document.forms.myform.elements.contact.value == "") 
    {
        alert("Please select contact medium..."); 
    }
}
</script>

<form name="myform" id="myform">
   <input type="radio" name="contact" id="contact" value="SMS">
   <label>SMS</label> <input type="radio" name="contact" id="contact" value="CALL">
   <label>CALL</label> <input type="radio" name="contact" id="contact" value="EMAIL">
   <label>EMAIL</label>

   <button onclick="SubmitIt();">Submit</button>
</form>