比如以下代码：

var res = fetch('/api/blog/detail/' + BlogGlobals.blogID).then(res => res.json())
        console.log(res);

可以返回正常结果，但是：

function clickBotton(){
        var res = fetch('/api/blog/detail/' + BlogGlobals.blogID).then(res => res.json())
        console.log(res);
        
    };

会报错

Uncaught (in promise) TypeError: Failed to fetch
    at HTMLButtonElement.clickBotton (userscript.html?id=f905148f-9aca-4422-95a1-bff3314b907d:27:19)
clickBotton @ userscript.html?id=f905148f-9aca-4422-95a1-bff3314b907d:27
Promise.then（异步）
clickBotton