Javascript code to implement CheckBox's all selection and deselection_form effects

The method introduced in this article has independent trigger conditions. It can select or unselect all CheckBoxes with a specified name. There can be multiple sets of CheckBoxes for all selections on the same page. It has sound functions and strong versatility.
Rendering:

Run to see the effect:

<input type="checkbox" name="test" value="" onclick="if(this.checked==true) { checkAll('test'); } else { clearAll('test'); }"> <input type="checkbox" name="test" value="a"> Select all letters switch <input type="checkbox" name="test" value="b"> a <input type="checkbox" name="test" value="c"> b <input type="checkbox" name="test" value="d"> c <input type="checkbox" name="test" value="e"> d <input type="checkbox" name="test" value="f"> e <input type="checkbox" name="test" value="g">f <br> g <input type="checkbox" name="num" value="" onclick="if(this.checked==true) { checkAll('num'); } else { clearAll('num'); }"> <input type="checkbox" name="num" value="1"> Digital all-select switch <input type="checkbox" name="num" value="2"> 1 <input type="checkbox" name="num" value="3"> 2 <br> 3 <br><input type="button" value="选择所有的字母" onclick="checkAll('test')"> <input type="button" value="清空选中的字母" onclick="clearAll('test')"> <br> <br><input type="button" value="选择所有的数字" onclick="checkAll('num')"> <input type="button" value="清空选中的数字" onclick="clearAll('num')">