HTML全选反选按钮实现方法

<div>
    <label for="check_all">全选：label>
    <input id="check_all" onclick="checkAll()" type="checkbox"/>
div>

<div>
    <label for="check_item">选择项：label>
    <input id="check_item1" name="check_item" type="checkbox" value="1"/>选项一
    <input id="check_item2" name="check_item" type="checkbox" value="2"/>选项二
    <input id="check_item3" name="check_item" type="checkbox" value="3"/>选项三
div>

<script>
    function checkAll() {
        var check_all = document.getElementById("check_all");
        var check_items = document.getElementsByName("check_item");
        for (var i = 0; i < check_items.length; i++) {
            check_items[i].checked = check_all.checked;
        }
    }
script>