单击重置按钮后如何删除Cookie？

我将复选框的选中状态保存在Cookie中。我想在单击“重置”按钮时将所有复选框重置为未选中状态。javascript我正在使用“重置”复选框，但是当我刷新页面时，检查状态又回来了。

HTML：

    <form method="GET" name="frm1" action="filter.php" id="form">
    <input type="reset" onclick="return resetForm();"/>

    <div  class="" style="display:inline-block; margin-left:15px;" >
        <label class="custom-control custom-checkbox">
        <input type="checkbox" class="custom-control-input ids" name="search[]" value="sub1">
        <span class="custom-control-indicator"></span>
        <span class="custom-control-description" >sub1</span>
        </label><br>

        <label class="custom-control custom-checkbox">
        <input type="checkbox" class="custom-control-input ids" name="search[]" value="sub2">
        <span class="custom-control-indicator"></span>
        <span class="custom-control-description">sub2</span>
        </label><br> 

    </div>  
    </form>  

脚本：

    <script> 

    document.addEventListener("DOMContentLoaded", function(event) {
    var chks = document.querySelectorAll('input[name="search[]"]');

    for (var i = 0; i < chks.length; i++) {
        if (getCookie('search[' + chks[i].value + ']') == 'true') {
        chks[i].checked = true;
        }
    }

    for (var i = 0; i < chks.length; i++) {
        chks[i].addEventListener('click', function() {
        document.cookie = "search[" + this.value + "]=" + this.checked + "; expires=Thu, 18 Dec 2018 12:00:00 UTC; path=/";
    });
    }

    function getCookie(cname) { 
    var name = cname + "=";
    var decodedCookie = decodeURIComponent(document.cookie);
    var ca = decodedCookie.split(';');
    for (var i = 0; i < ca.length; i++) {
    var c = ca[i];
    while (c.charAt(0) == ' ') {
      c = c.substring(1);
    }
    if (c.indexOf(name) == 0) {
      return c.substring(name.length, c.length);
    }
    }
    return "";
    }
    });

    function resetForm() {

    var expired = new Date(today.getTime() - 24 * 3600 * 1000); // less 24 hours

    function deleteCookie(name)
    {
    document.cookie=name + "=null; path=/; expires=" + expired.toGMTString();
    }
    }
    </script>

我在这里做什么错？请帮我。