How to get value of selected radio button?

var rates = document.getElementById('rates').value;

The rates element is a div, so it won't have a value. This is probably where the undefined is coming from.

The checked property will tell you whether the element is selected:

if (document.getElementById('r1').checked) {
  rate_value = document.getElementById('r1').value;
}

$("input[type='radio'][name='rate']:checked").val();

This works in IE9 and above and all other browsers.

document.querySelector('input[name="rate"]:checked').value;

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