在每input 加上 required 監聽 oninput=”renderCheckbox('checkbox');” checkbox：input 的 name

<div class="form-check form-check-inline">
                <input type="checkbox" name="checkbox" value="複選1" class="form-check-input checkbox" id="checkbox_0" required="" oninput="rendeCheckbox('checkbox');">
                <label class="form-check-label" for="checkbox_0">複選1</label>
              </div>
<div class="form-check form-check-inline">
                <input type="checkbox" name="checkbox" value="複選2" class="form-check-input checkbox" id="checkbox_1" required="" oninput="rendeCheckbox('checkbox');">
                <label class="form-check-label" for="checkbox_1">複選2</label>
              </div>

函式

		function renderCheckbox(name){
      if(isAtLeastOneChecked(name)){
        removeRequired(name);
      }else{
        setRequired(name);
      }
    }

    function isAtLeastOneChecked(name) {
      let checkboxes = Array.from(document.getElementsByName(name));
      return checkboxes.some(function(item) {
        return item.checked;
      });
    }

    function removeRequired(name){
      let checkboxes = Array.from(document.getElementsByName(name));
      for(let i in checkboxes){
        checkboxes[i].removeAttribute('required');
      }
    }
    function setRequired(name){
      let checkboxes = Array.from(document.getElementsByName(name));
      for(let i in checkboxes){
        checkboxes[i].setAttribute('required', true);
      }
    }