Functions between certain times of the day

Question

I'm working on something for my school's laptops that will disable videos/games between 8:00 AM and 3:15 PM. Due to the giant time gap, I will not be waiting to see if the code functions properly or not. What I want to know is if my code will function properly, as I'm not good enough at JavaScript to know myself.

function timer() {
 var date = new Date();
 var hours = date.getHours();
 var minutes = date.getMinutes();
 if (minutes < 10) {
 var minutes = "0" + minutes;
 } else {}
 $(".time").html(hours + ":" + minutes),
 setInterval(timer, 1000);
 // Disable stuff
 if (hours > 8 & hours < 15) {
 $("video").hide();
 $("video").parent().html("<b>Can you do us all a favor and not eat up all the bandwidth with your video watching?</b>" + "<br/>" + "<b>Thank you!</b>" + "<br/>" + "<br/>");
 $("embed").hide();
 $("embed").parent().html("<b>This is no time for childish games.</b>" + "<br/>" + "<b>Shouldn't you be studying or doing something related to school?</b>" + "<br/>" + "<br/>");
 } else if(hours > 15 & hours < 8) {
 $("video").show();
 $("embed").show();
 }
}

• Evan Bechtol: In your first if statement, you put the semi-colon at the end of the else. I mean it works, but it's just really strange looking and looks like an error to anyone besides yourself. I don't see a reason to not just place it at the end of the line it's intended for. Also, it goes against the seemingly apparent convention that you have setup throughout your code.
• thrifus: @EvanBechtol Thanks for the help. I think it looks strange now that you mention it.
• Evan Bechtol: Ah much better, my code-ocd has calmed itself now.
• vmariano: About the idea: I think is really hard generat a lock from javascript, specially for client side, is very easy to skip. You should block with a proxy + some crazy script who block this type of content. You shuld ask in super user or something like that. about the test your code, you can "simulate" the time. with a new Date custom, configure outside of the range.

Answer 1

I will comment on this part...

if (hours > 8 & hours < 15) {
 $("video").hide();
 $("video").parent().html("<b>Can you do us all a favor and not eat up all the bandwidth with your video watching?</b>" + "<br/>" + "<b>Thank you!</b>" + "<br/>" + "<br/>");
 $("embed").hide();
 $("embed").parent().html("<b>This is no time for childish games.</b>" + "<br/>" + "<b>Shouldn't you be studying or doing something related to school?</b>" + "<br/>" + "<br/>");
} else if(hours > 15 & hours < 8) {
 $("video").show();
 $("embed").show();
}

As Hosch said, you should be using the conditional operator &&.

Also, the else if clause wouldn't work because (hours > 15 && hours < 8) is only true if hours > 15 AND hours < 8, so it's never true. What you want is the conditional "or" operator: if (hours > 15 || hours < 8). But you don't even need to specify that if what you want is just to cover all the other cases: "if it's between 8 AM and 3:15 PM do this, otherwise do that".

So...

else { ... }

looks better.

Finally, hours > 8 && hours < 15 would only be true between 9 AM and 2 PM (instead of between 8 AM and 3 PM) as you're using the "greater than" (>) and "lesser than" (<) operators instead of "greater or equal" (>=) and "lesser or equal" (<=).

In order to cover the whole range you specified, you should write something like:

if ((hours >= 8 && hours < 15) || (hours == 15 && minutes <= 15)) { ... }

Answer 2

First of all, this looks like dead code:

if (minutes < 10) {
 var minutes = "0" + minutes
} else {}

The if doesn't do anything except assign a variable that immediately goes out of scope, and the else doesn't do anything at all.

---

Right here, I'm not sure why you use the logical & when you don't need it. You should be using the conditional && operator instead:

if (hours > 8 & hours < 15) {
 $("video").hide();
 $("video").parent().html("<b>Can you do us all a favor and not eat up all the bandwidth with your video watching?</b>" + "<br/>" + "<b>Thank you!</b>" + "<br/>" + "<br/>");
 $("embed").hide();
 $("embed").parent().html("<b>This is no time for childish games.</b>" + "<br/>" + "<b>Shouldn't you be studying or doing something related to school?</b>" + "<br/>" + "<br/>");
} else if(hours > 15 & hours < 8) {
 $("video").show();
 $("embed").show();
};

As for working, it appears that it will work - until a student figures out what is happening and turns the script off. I am not a JS expert, though, and I do not have the full context of how this will be run, so you should get another opinion. Personally, I would set it up and test it thoroughly over a day or so before deploying it.

• thrifus: Thanks for the help. I've removed the else {}, changed the &s to && and I'm only using the var minutes = "0" + minutes; becuase I want a 0 to be added in front of 1-9 so it looks better. I don't know any other way to do it and it seems to be working, but if you have another way to do it feel free to tell me. I will be creating Google Chrome, Safari, and Firefox extensions that are managed.

Answer 3

In addition to the errors pointed out above, your recursive call of setInterval() in timer() is going to set off \$ 2^t \$ new intervals every second so that by time \$t\$ you have a total number of intervals running of $$ 1+ \sum\limits_{n = 0}^t 2^n = 2^{t+1}$$ This may lead to some memory management issues overtime and cause the browser to crash.

If you still choose to go with the .js route, I propose a rewrite:

var poll = setInterval(timer, 1000);
function timer () {
 var date = new Date();
 var hours = date.getHours();
 var minutes = date.getMinutes();
 var minuteString = minutes < 10? "0" + minutes: minutes;
 $(".time").html(hours + ":" + minuteString);
 var now = new Date(2000, 01, 01, hours, minutes, 0);
 var start = new Date(2000, 01, 01, 8, 0, 0);
 var end = new Date(2000, 01, 01, 15, 0, 0);
 var disable = start <= now && now <= end;
 if (disable) {
 // Disable video
 } else {
 // Enable video
 }
 //return disable;
}

• thrifus: I have no idea what that formula is, but thanks for your help. It seems like it loads faster now.