nodejs firebase错误RangeError:超出最大调用堆栈大小的失败 [英] nodejs firebase error RangeError: Maximum call stack size exceeded failure

问题描述

我的firebase出现了错误:

I have an error from the firebase :

FIREBASE警告:用户回调引发了异常. RangeError:超出了最大调用堆栈大小

FIREBASE WARNING: Exception was thrown by user callback. RangeError: Maximum call stack size exceeded

我没有发现我的错误.

我在这里很迷路，请帮助.

I'm very lost in here, please help.

我的代码如下:

app.post('/updateCoords', (req, res)=>{
    var usrID = req.body.id;
    var usrCoords = {
        lat: req.body.lat,
        long: req.body.long
    }
    console.log('userID : '+usrID+' lat : '+usrCoords.lat+' long : '+usrCoords.long);
    var ref = database.ref('users');
    try{
        ref.orderByChild('username').equalTo(usrID).on("value", (snapshot)=> {
            if(!snapshot.val()){
                // Error
                return res.json({msg: 'username is not in D.B', success: false});
            }
            // Success
            admin.database().ref('users/' + usrID + '/currentLocation').update({
                lat: usrCoords.lat,
                long: usrCoords.long
            });
            return res.json({msg: 'user coords changed', success: true});
        });
    }catch(ex){
        console.log('ex /updateCoords = '+ex);
    }
});

推荐答案

您正在更新要读取的同一节点.这将导致on("value"回调再次被触发.然后依次写入一个新值，该值再次触发回调.这一直持续到运行时用完调用堆栈空间为止.

You're updating the same node that you're reading. This causes the on("value" callback to be triggered again. Which in turn then writes a new value, which trigger the callback again. And that continues until the runtime runs out of call stack space.

最简单的解决方案是使用once()代替on():

The simplest solution is to use once() instead of on():

   var ref = database.ref('users');
    try{
        ref.orderByChild('username').equalTo(usrID).once("value", (snapshot)=> {
            if(!snapshot.val()){
                checker = true;
            }

            if(snapshot.val()){
                admin.database().ref('users/' + usrID + '/currentLocation').update({
                    lat: usrCoords.lat,
                    long: usrCoords.long
                });
                return res.json({msg: 'user coords changed', success: true});
            //  checker = false;
            }


            // res.json({msg: 'username is not in D.B', success: false});

        });
    }catch(ex){
         console.log('ex /updateCoords = '+ex);
    }

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