How to make checkboxes behave like radios dependant on classname

HTML

<table>
  <tr>
    <th>
      Early Morning<br>
      <small>6am-9am</small>
    </th>
    <td>
      <input type="checkbox" class="earlyMorning" name="field_807[]" id="field_871_0" value="Early Morning 6am-9am Monday" />
    </td>
    <td>
      <input type="checkbox" class="lateMorning" name="field_807[]" id="field_872_1" value="Early Morning 6am-9am Tuesday" />
    </td>
    <td>
      <input type="checkbox" class="earlyAfternoon" name="field_807[]" id="field_873_2" value="Early Morning 6am-9am Wednesday" />
    </td>
    <td>
      <input type="checkbox" class="lateAfternoon" name="field_807[]" id="field_874_3" value="Early Morning 6am-9am Thursday" />
    </td>
    <td>
      <input type="checkbox" class="earlyEvening" name="field_807[]" id="field_875_4" value="Early Morning 6am-9am Friday" />
    </td>
    <td>
      <input type="checkbox" class="lateEvening" name="field_807[]" id="field_876_5" value="Early Morning 6am-9am Saturday" />
    </td>
    <td>
      <input type="checkbox" class="overnight" name="field_807[]" id="field_877_6" value="Overnight 12am-6am Sunday" />
    </td>
  </tr>
  <tr>
    <th>
      Late Morning<br>
      <small>9am-12pm</small>
    </th>
    <td>
      <input type="checkbox" class="earlyMorning" name="field_807[]" id="field_878_7" value="Late Morning 9am-12pm Monday" />
    </td>
    <td>
      <input type="checkbox" class="lateMorning" name="field_807[]" id="field_879_8" value="Late Morning 9am-12pm Tuesday" />
    </td>
    <td>
      <input type="checkbox" class="earlyAfternoon" name="field_807[]" id="field_880_9" value="Late Morning 9am-12pm Wednesday" />
    </td>
    <td>
      <input type="checkbox" class="lateAfternoon" name="field_807[]" id="field_881_10" value="Late Morning 9am-12pm Thursday" />
    </td>
    <td>
      <input type="checkbox" class="earlyEvening" name="field_807[]" id="field_882_11" value="Late Morning 9am-12pm Friday" />
    </td>
    <td>
      <input type="checkbox" class="lateEvening"...

JavaScript

/// this code will not work with older versions of Internet Explorer
/// you will need a polyfill for addEventListener, or implement conditionals
/// to use attachEvent instead.

window.addEventListener('load', function(){
    var inps = document.getElementsByTagName('input'), inp;
    var i, l = inps.length, c;
    var groups = {};
    var react = function(e){
      var inp = e.target, group = groups[inp.className], i, l, otherinp;
      if ( group ) {
        for ( i=0, l=group.length; i<l; i++ ) {
          otherinp = group[i];
          if ( inp !== otherinp ) {
            otherinp.checked = false;
          }
        }
      }
    };
    /// group inputs based on className
    for ( var i=0; i<l; i++ ) {
        if ( (inp = inps[i]) && inp.type == 'checkbox' ) {
            switch( (c = inp.className) ) {
              case 'earlyMorning':
              case 'lateMorning':
              case 'earlyAfternoon':
              case 'lateAfternoon':
              case 'earlyEvening':
              case 'lateEvening':
              case 'overnight':
                !groups[c] && (groups[c] = []);
                groups[c].push(inp);
                inp.addEventListener('change', react);
              break;
            }
        }
    }
});