From "You Don't Know JS Yet" Appendix B

Practicing Closure

function range(start, end){
    if(end != undefined){
        if(start <= end){
            return getRange(start, end);
        }else{
            return 0;
        }
    }else{
        return function innerFunction(innerVariable){
            if(start <= innerVariable){
                return getRange(start,innerVariable);
            }else{
                return 0;
            }
        }
    }

    function getRange(start, end){
        let arr = [];
    
        for(let i = start; i <= end; i++){
            arr.push(i);
        };
        return arr;
    }
}


range(3, 3); // [3]
range(3, 8); // [3,4,5,6,7,8]
range(3, 0); // []

var start3 = range(3);
var start4 = range(4);

start3(3); // [3]
start3(8); // [3,4,5,6,7,8]
start3(0); // []

start4(6); // [4,5,6]

Practicing Comparisons

const dayStart = "07:30";
const dayEnd = "17:45";

const getTimer = startTime => ({
    Start: {
        hour: +`${[...dayStart][0]}${[...dayStart][1]}`,
        minute: +`${[...dayStart][[...dayStart].length - 2]}${[...dayStart][[...dayStart].length - 1]}`
    },
    End: {
        hour: +`${[...dayEnd][0]}${[...dayEnd][1]}`,
        minute: +`${[...dayEnd][[...dayEnd].length - 2]}${[...dayEnd][[...dayEnd].length - 1]}`
    },
    GivenTime: (() => {
        if([...startTime].length == 4){
            return {
                hour: +`${[...startTime][0]}`,
                minute: +`${[...startTime][[...startTime].length - 2]}${[...startTime][[...startTime].length - 1]}`
            }
        }else{
            return {
                hour: +`${[...startTime][0]}${[...startTime][1]}`,
                minute: +`${[...startTime][[...startTime].length - 2]}${[...startTime][[...startTime].length - 1]}`
            }
        }
    })(),
})

function scheduleMeeting( startTime, duration ){
    const time = getTimer(startTime);

    if(time.GivenTime.hour == time.Start.hour){
        if(time.GivenTime.minute >= time.Start.minute){
            return true;
        }else{
            return false;
        }
    }else if(time.GivenTime.hour > time.Start.hour && time.GivenTime.hour < time.End.hour){
        return true;
    }else if(time.GivenTime.hour == time.End.hour){
        // console.log("I'm here!");
        if((time.GivenTime.minute + duration) <= time.End.minute){
            // console.log(time.GivenTime.minute + duration);
            return true;
        }else{
            // console.log(time.GivenTime.minute + duration);
            return false;
        }
    }else{
        return false;
    }
}

scheduleMeeting("7:00", 15); // false
scheduleMeeting("07:15", 30); // false
scheduleMeeting("7:30", 30); // true
scheduleMeeting("11:30", 60); // true
scheduleMeeting("17:00", 45); // true
scheduleMeeting("17:30", 30); // false
scheduleMeeting("18:00", 15); // false