Execute Function on specified time.

tMinus.js

/* ============================================= *

    queue to fire today       ╭∩╮（︶︿︶）╭∩╮

 * ============================================= */


function triggerOnTime(cb, hour, minute, pm) {
    var config = {
            // set to noon as default
            hour: hour || 12,
            min: minute || 0,
            sec: 59,
            ms: 100
        },
        // get current time
        __NOW__ = new Date(),
        targetTime,
        triggerTime,
        tMinus;

    if (typeof cb !== 'function') {
        // not valid function to set
        return;
    }

    // add for Post Meridiem
    if (pm) {
       config.hour += 12; // add 12 hours for a pm time
       if (config.hour === 24) {
           config.hour = 0;
       }
    }

    // calc trigger time
    targetTime = new Date(__NOW__.getFullYear(), __NOW__.getMonth(), __NOW__.getDate(), config.hour, config.min, 0, 0);

    // get a head of race!
    // roll back 900 ms
    --config.min;
    if (config.min < 0) {
        config.min = 59;
        --config.hour;
    }

    // calc augmented trigger time
    triggerTime = new Date(__NOW__.getFullYear(), __NOW__.getMonth(), __NOW__.getDate(), config.hour, config.min, config.sec, config.ms);

    // get countdown time
    tMinus = triggerTime - __NOW__;

    if (tMinus < 0) {
        tMinus += 86400000; // it's after the time, try tomorrow.
    }

    setTimeout(function() {
        cb({
            'time': targetTime,
            'countdown': tMinus
        });
    }, tMinus);

    return tMinus;
}

// example of use * ---- > 
// time as 24:00 or use 'pm' flag
// 4:20pm // all below are valid

// triggerOnTime(fn(){}, 6, 20);
// triggerOnTime(fn(){}, 4, 20,  true);
// triggerOnTime(fn(){}, 4, 20, 'pm');

triggerOnTime(function(info) {
    // `info.time` and `info.countdown` if you need'em
    var msg = 'The time is: ' + info.time + '\r';
    info.countdown = info.countdown / 1000;
    msg += 'This was initiated ' + info.countdown + ' seconds ago.';
    alert(msg);
}, 4, 20, 'pm');