Question

Perhaps it is very basic, but I have some issue with the radios.length property. I have some input like so :

<input type="radio" name="name1" value="test1" checked='checked'/><br />
<input type="radio" name="name2" value="test2" checked='checked'/><br />

When I alert the radios.length property, I always have 0 as an answer. Could someone explain why ?

Answer 1

radios.length is not a valid property in the DOM..
You need to find those(which are input in this case) and then use the length property on it ..

var radios = document.getElementsByTagName("input") ;

alert(radios.length) // this will alert the correct value

UPDATE

To Select only the Radio buttons you can do this

var radios = document.getElementsByTagName("input") ;
var checkBoxes = [];

for(​var i =0, len = radios.length; i< len;i++){
    if(radios[i].type === 'radio'){
        checkBoxes.push(radios[i]);
    }
};

console.log(checkBoxes)​

Check Fiddle

Also if you are using jQuery do not forget to encase your script in DOM Ready handler

jQuery

$('#radio1').attr('type') // Need to use the .attr() method

jQuery Fiddle