在javascript中将cookie值解析为if/else if

Question

所以我有一个简单的会话 cookie 检索器，并将 cookie 值写入页面。只有两个值，“是”和“否”，否则返回 null。目前，它检查是否有值，如果有，则将该值写入页面。如何告诉脚本有条件地写入值（即，写入“是”，因为该值是“是”，与“否”相同，而不是仅仅传递响应）而不是它是否存在？

<script>
function readCookie(name) {
    var nameEQ = name + "=";
    var ca = document.cookie.split(';');
    for(var i=0;i < ca.length;i++) {
        var c = ca[i];
        while (c.charAt(0)==' ') c = c.substring(1,c.length);
        if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
    }
    return null;
};
</script>

...

<p>
Response 1: 
<script>
var res1 = readCookie('res1')
if (res1) {
    document.write('res1')
}
else {
document.write("You did not respond.")
};
</script>
</p>

Answer 1

function getCookie(name) {
    var matches = document.cookie.match(new RegExp(
      "(?:^|; )" + name.replace(/([\.$?*|{}\(\)\[\]\\\/\+^])/g, '\\$1') + "=([^;]*)"
    ))
    return matches ? decodeURIComponent(matches[1]) : undefined
}

document.write(getCookie('res1') != undefined ? 'res1' : 'You did not respond.')