if / else errors - learn how to fix these

else is not allowed to have a condition

@AlbionsRefuge - Great post!!

I’ve also noticed a few people trying to do things like…

if ( a < b) {
    do something here;
}
else if (a > b) {
    do this other thing;
}
else (a == b) {
    do something different;
}

and then they post a question asking what is wrong with their code.

It seems that they aren’t grasping a few concepts about the flow of logic in if / else if / else statements.

So I thought this would be a great place to point out a few things that those struggling with if / else if / else might find helpful.

For one thing, unlike if and else if, an else statement is not used to do condition checking. The purpose of else is to execute alternative code in the situation where the if, and else if conditions return false.

In the particular code example above, if the program execution has reached the else statement it means that:

a < b returned false and a > b also returned false.

If the value of a is: not greater than the value of b and not less than the value of b, then it logically follows that the value of a must be equal to the value of b! because there is no other option for what the value of a could be.

There is no need to even bother trying to test for ( a == b ). You simply have the else statement do something.

The correct code would be:

if ( a < b) {
    do something here;
}
else if (a > b) {
    do this other thing;
}
else {
    do something different;
}

I think those of us who are seasoned programmers (or people like me who have just had some exposure to programming concepts and have coded up a few personal projects) tend to take these things for granted.

Pointing them out might seem very elementary to experienced programmers. However, beginners who have never dealt with these concepts can and do struggle with these kinds of ideas and I felt a good explanation might be in order.

I hope this is a helpful comment!

Conditions, Blocks and Semicolons

The most simple conditional statement (1) looks like this:

if(condition)
   statement;

Here statement is exactly 1 statement. In case you want an alternativ to the if you can extend it with an else (2):

if(condition)
   statement;
else
   statement2;

Again statement and statement2 are only one statement (each). But what about using more than one statement in a case? (3)

if(condition)
   statement1;
   statement2;

here statement1 would belong to the condition and statement2 would be executed without condition. (4)

if(condition)
   statement1;
   statement2;
else
   statement3;

And here it would get even worse, as the else needs to follow directly after the statement of the if or they will not be treated as connected and you get an error as an else doesn’t make sense without an if.

So how can we use more than one statement per case, what are these {} we usually use and why should we even bother about these cases mentioned above?

Well to have more than one statement per case we use the trick of working with blocks of code which start with { and end with } these blocks count as one statement regardless of the number of statements which are inside.(*)

The reason why we should have a look at this although you could be perfectly fine by using blocks all the time even if they are not necessary is that we every now an then may encounter one of the errors described above which are related to this ability.

e.g. a semicolon:

When you put a semicolon at the end of a condition, like this: if (choice1 === choice2); you are telling the interpreter to consider that as the end of your if statement. Any code following that will be processed without regard for the outcome of that if condition.

That’s pretty close, but the semicolon doesn’t end the if statement itself, it ends the statement of the if. This might be confusing, but have a look at (1) and you could see that if(condition); just means:

if(condition)
  /*empty space*/;

so the semicolon creates an empty statement by ending the “nothing” after the condition which would normaly be ignored and now the condition is either finished or an else needs to follow directly after it, but mostly it was just a mistake and it goes like this: if(condition);{...} and then you end up at the error described in (4).

Another use of this feature is that a conditional statement counts as one statement aswell, which lets us create an else if case by nesting:

if(condition)
  statement;
else
  if(condition2)
    statement2;
  else
    statement3;

could be formatted to:

if(condition)
  statement1;
else if(condition2)
  statement2;
else
  statement3;

(*) {} are used as blocks of codes for conditions and loops, functions and objects may use them in a different way.

Are you getting one of the errors on the list at the top of this thread but following the troubleshooting steps isn’t helping? Show us all of your code using the “Add an answer” box, tell us the EXACT error message and we’ll look into it!

Very useful - thanks!

@Mark: The error you explained is also caused by this only-one-statement-after-a-conditional-case-rule. At first you are absolutly right about the fact that else does not need a condition! But the error in the code is not that else has “condition” but that there are two statements on one line (without separator):

else (a == b) {
    do something different;
}

first statement is the a == b, which is a pretty pointless statement as it is just true or false and is neither stored nor printed (as said, else doesn’t expect a condition, so the () don’t show any relation to else but just increase the priority of evaluating the stuff inside, which is unnecessary as this code would follow anyway) and the second statement is the begining of the block.

So if you had used:

else (a == b) 
{
    do something different;
}

or

else (a == b); {
    do something different;
}

it would still be pointless and missleading as the code in the block would be evaluated in any case, but syntactically it would be correct.

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(5);

SyntaxError: Unexpected token ILLEGAL

also stuck with unexpected token pls what is wrong with this code 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 (5);

Hey, i’m not sure what’s wrong with the code. The error I’m getting is “unexpected token else”

var compare = function(choice1, choice2) { if (choice1 === choice2) { return “The result is a tie!”; } else if (choice1 === “rock”) { if (choice2 === “scissors”) { return “rock wins”; } else { return “paper wins”; } };

    else if (choice1 === "paper") {
        if (choice2 === "rock") {
            return "paper wins";
        } 
        else {
            return "scissors wins";
        }
    };

};

PS: I’ve figured it out. I only needed that final semi-colon after the last closing brace, not the ones after the else if closing brace.