CODEWITHSUNDEEP
javascriptjquerymeteormeteor-blaze
Marius Alchimavičius
Marius Alchimavičius

Reputation: 43

Alternative for setInterval() database checking -> Meteor.js

The idea is pretty simple I need to do scroll-down message feed when number of records is changed or when new message is inserted into doc (same thing).

Current implementation uses set interval to keep checking for db changes:

Template['messenger'].onCreated(function(){
    $(function(){
        Template['messenger'].methods.scrollOnNewMessages().start();
    })
});

Template['messenger'].methods = {

    scrollOnNewMessages : function () {
        return {
            oldCount : 0,

            start : function () {
                this.oldCount = Messages.find().count();
                setInterval(this.funcToRepeat, 400);
            },

            funcToRepeat : function () {
                var newCount = Messages.find().count();
                var updated = this.oldCount !== newCount;
                if(updated){
                    this.oldCount = newCount;
                    Template['messenger'].methods.scrollDown();
                }
            }

        }
    },

    scrollDown: function () {
        var height = $(".messageEntry").outerHeight() + 3;
        var scrollLength = $('.messageEntry').length * height - $("#messageFeed").height();
        $('#messageFeed').animate({scrollTop:scrollLength}, 400, 'swing');
    },
}

This works pretty well, but I hate the idea of using setInterval(). Tried doing this with Template.my_template.onRendered but this will execute a function on every template that was rendered that means if I have 50 messages rendered on startup it will auto-scroll 50 times without much purpose.

So can you guys think of a better CLEAN solution without using setInterval ?

Upvotes: 0

Views: 134

Answers (1)

David Weldon
David Weldon

Reputation: 64312

You can just use an autorun inside of your onRendered callback:

Template.messenger.onRendered(function() {
  this.autorun(function() {
    if (Messages.find().count())
      Template.messenger.methods.scrollDown();
  });
});

Because the count is reactive, the autorun will fire every time it changes. Try adding that and removing scrollOnNewMessages and its reference in onCreated.

Upvotes: 2

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