获取火基函数的平均值，找到所需节点的平均值

Question

我想从实时数据库中的数据库中平均我想要的字段并将它们放在另一个节点上

exports.taverage = functions.database.ref('/User/tsetUser/monthQuit/{pushId}')
    .onCreate((snapshot, context) => {
        return admin.database().ref('/User/tsetUser/monthQuit/{pushId}/quitTime').once('value')
            .then(function(snapshot) {
                let sum=0;
                snapshot.forEach(child => {
                    sum = sum + child.val();
                })
                let avg = sum / snapshot.numChildren();

                return admin.database().ref('/User/tsetUser/inform/standardQuit').set(avg);
            });
    });

错误：Reference.set 失败：第一个参数在 propertyenter image description here 中包含 NaN

Answer 1

我的理解是.numChildren() 实际上应该是.getChildrenCount()，如in the documentation 所述。

另外，请考虑通过执行以下操作来修改您的代码以解决“除以零”的情况：

functions.database.ref('/User/tsetUser/monthQuit/{pushId}')
.onCreate((snapshot, context) => {
    return admin.database().ref('/User/tsetUser/monthQuit/{pushId}/quitTime').once('value')
    .then(function(snapshot) {

        /* Get children could via getChildrenCount() */
        let divisor = snapshot.getChildrenCount();

        /* Ensure divisor is greater than zero to avoid
        divide by zero case */
        if(divisor > 0) {

            let sum=0;

            snapshot.forEach(child => {
                sum = sum + child.val();
            })
            let avg = sum / divisor;

            return admin.database().ref('/User/tsetUser/inform/standardQuit').set(avg);
        }

    });
});