Javascript beginner: What am I doing wrong? Why does it say that keyword is wrong? [on hold]

I need to use an if/else statement. I also need to call the function at the very end using the numbers 10, 5 and 8. Can someone please tell me what I did wrong?

var sleepCheck= function(numHours)
{
    if(sleepCheck => 8)
    {
        return "You're getting plenty of sleep! Maybe even too much!";
    };
    else {
        return "Get some more shut eye!";
};