Get the value of the checked checkbox or radio.

getCheckedValue.js

/**
 * Get the value of the checked checkbox(s) or radio.
 * @param {Element} inputs the input:checkbox or input:radio elements
 * @return {String|Array} the checkec value
 */
function getCheckedValue(inputs) {
  var val;
  var len = inputs.length;
  
  if (inputs[0].type === 'checkbox') {
    val = [];
    
    for (var i = 0; i < len; i++) {
      if (inputs[i].checked) val.push(inputs[i].value);
    }
  } else {
    val = null;
    
    for (var i = 0; i < len; i++) {
      if (inputs[i].checked) {
        val = inputs[i].value;
        break;
      }
    }
  }
  
  return val;
}