code: function initCheckBox(elem, parsed){
    var self = this;
    var watcher = this.$watch(parsed, function(newValue){
      dom.attr(elem, 'checked', !!newValue);
    }, STABLE);
  
    var handler = function handler(){
      var value = this.checked;
      parsed.set(self, value);
      watcher.last = value;
      self.$update();
    }
    if(parsed.set) dom.on(elem, "change", handler)
  
    if(parsed.get(self) === undefined){
      parsed.set(self, !!elem.checked);
    }
  
    return function destroy(){
      if(parsed.set) dom.off(elem, "change", handler)
    }
  }
docs: input:checkbox  binding