将变量传递给回调-Node.js

Question

I'm creating a simple Messenger bot, using unofficial Facebook Chat API ( https://github.com/Schmavery/facebook-chat-api ) and Node.js.

For now, I'm working on sending messages to specific users, on a specific time. Here's part of my code:

if(msgdate.getTime() <= currdate.getTime()){

    console.log(alarms[i].message);
    // output: test

    api.getUserID(alarms[i].user, (err, users) => {
        if(err) return console.error(err);

        api.sendMessage(alarms[i].message, users[0].userID);
        // TypeError: Cannot read property 'message' of undefined
    });
}

And, my question is: how could I pass alarms array to this callback, so I'd be able to send message to a specific user?

Answer 1

Looks like that you change i variable somewhere, and because of that when callback is called alarms[i] is undefined. You need to store alarms[i] in a new variable and use it in callback:

let alarm = alarms[i];
api.getUserID(alarm.user, (err, users) => {
  if(err) {
    return console.error(err);
  }
  api.sendMessage(alarm.message, users[0].userID);
});

Answer 2

Appear that you are using for loop outside. Try pass your var that way:

var alarm = alarm[i];
(function (alarm) {
    if(msgdate.getTime() <= currdate.getTime()){

    console.log(alarm.message);
    // output: test

    api.getUserID(alarm.user, (err, users) => {
        if(err) return console.error(err);

        api.sendMessage(alarm.message, users[0].userID);
        // TypeError: Cannot read property 'message' of undefined
    });
})(alarm);

Maybe you need to pass other vars too. Just put a comma and other var, example:

(function (alarm, user){
    // your code here
})(alarm, user);