Script to measure the passage of time?

Question

I'm currently developing a small game for a class using Crafty, and our game requires the passage of time. To give context, it's a tamagotchi-like game where the player controls a creature and feeds it, grooms it, etc., when required, so we need to measure time for things such as "every five minutes the creature will be hungry" or "after a certain amount of time (say, 20 minutes) the creature will die of natural causes and the game will end". My problem is that I'm not sure what is the best way to go about this. Should I use setInterval? setTimeout? My own timer class? I don't know what's the most common solution for instances like these. So far I've tried the first two options without successful results.

I also tried looking for any crafy functions for time; and the closest I could find was Crafty.bind("EnterFrame", function() { ... }), so I could 'manipulate' time frame by frame, but this didn't work either. Thanks in advance.

Answer 1

When the game starts, get a timestamp with new Date().getTime(), and keep it in a variable. On regular intervals (you can use setInterval), compare that with the current timestamp, and act according to how much time has passed.

I suggest building an array with the timed events, and checking its elements from the timer callback. Something like this:

var startTime = new Date().getTime();

// List of timed events
// (times are in milliseconds)
var events = [
    { time: 5000, text: "do something after 5 secs"},
    { time: 10000, text: "do something after 10 secs"},
    { time: 20000, text: "do something after 20 secs"}
];

// Check for events every second
setInterval(function() {
    var timePassed = new Date().getTime() - startTime;
    console.log("passed: " + timePassed + " milliseconds");

    // Check all events
    for(var i=events.length-1; i>=0; i--) {

        // If an event has expired, remove it from the list,
        // (and do whatever tou need to do)
        if(events[i].time <= timePassed) {

            // log the event text to the console
            console.log(timePassed + "ms passed. " + events[i].text);

            // remove from array
            events.splice(i, 1);
        }
    }

}, 1000);

DEMO (open your browser console to see the output).