Using Functions with Returns and If / Else Statements

jsFiddle Demo

Change your JavaScript to the following:

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

console.log(sleepCheck(10));
console.log(sleepCheck(5));
console.log(sleepCheck(8));

Description:

There were multiple issues with syntax, using a ; when not at the end of a line of code but rather the end of an if declaration. Also there was some issue with the if and else logic. Also inside the function you should be using numHours as that's the parameter of the function while sleepCheck is the function itself and won't make sense to use.

Note: I used console.log on the 3 function call to make debugging easier. Feel free to call the function any way you want.

Detailed Errors

//This line is perfect
var sleepCheck = function(numHours) 
{
    //This line shouldn't end in a ; as it is invalid syntax you are opening an if also should use the function parameter of numHours not sleepCheck
    if (sleepCheck >= 8);
    //this line isn't reached because of the above error there isn't an error here
    return "You're getting plenty of sleep! Maybe even too much";
//This also doesn't need to have a ; and shouldn't be closing the } as you are ending the function here
}; 
//This is now ignored because of the above but is good, doesn't line up with the above if because of the }; which should just be a }
else 
{
    //All good
    return "Get some more shut eye!";
}

sleepCheck(10);
sleepCheck(5);
sleepCheck(8);

The semi-colon at the end of the if statement is declaring that the statement is done. Get rid of it (the one on line 5) and it should work.

I used 'else if' because in the instructions it said Otherwise (else) if the number of hours of sleep is less than 8, have the computer return "Get some more shut eye!"; So I assumed I needed to. It worked though. shrugs

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

console.log(sleepCheck(10));
console.log(sleepCheck(5));
console.log(sleepCheck(8));

You need to remove the semicolon after the if statement: if (sleepCheck >= 8); <---

Here's a useful rule to keep in mind:

In JavaScript never place a semicolon just before an opening curly brace or an opening parentheses because it will make the parser jump over the code block that follows.

None of the above solutions worked for me. Here is one that really works:\

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

sleepCheck(10);
sleepCheck(5);
sleepCheck(8);

On lines 3 and 5, delete the semicolon. They are causing your else syntax error. Make sure you include a semicolon on line 9 to end the function as per the instructions in the Code Academy lesson.