javascript - 从 firebase 获取值

Question

我想获取 firebase 中函数之外的值以供全局使用，但它不起作用。

var ref = new Firebase("https://xxxxx.firebaseio.com/users/xxxx/roles/admin/"); // true or false

    ref.once("value", function(snapshot) {
    console.log("here");
    console.log(snapshot.val());
    var isAdmin = snapshot.val();
    return isAdmin;
});

console.log(isAdmin); /// cannot get value

Answer 1

您不能在外部使用isAdmin，因为它不可用，请在回调中使用它

ref.once("value", function(snapshot) {
    //You should wrap you code here, to use isAdmin variable
    //You can do whatever with isAdmin, but you can't return it.
    //It's callback that running asynchronously
    console.log(isAdmin)
})