Can I prevent stupid errors in JavaScript because the language does not require semicolons?

I just lost quite a bit of time because I changed a JavaScript function that read (something like)

function F(a,b,c) {

    return x(a,b,c) +
      开发者_StackOverflow中文版     y(a,b,c) + 
           z(a,b,c);
}

to

function F(a,b,c) {

    return // x(a,b,c) +
           y(a,b,c) + 
           z(a,b,c);
}

when I needed to test something.

The changed function returns undefined, of course, because the language does not require a semicolon and assumes the return to be a complete statement.

Unfortunatly, when I commented out x(a,b,c) I didn't think of this implication. So, is there a way to prevent such stupid misstakes in the future.

---

Lazy debugger's solution:

function F(a,b,c) {
    return (
      // x(a,b,c) +
      y(a,b,c) + 
      z(a,b,c)
    );
}

---

JSLint and a unit testing framework.

Problem at line 3 character 11: Expected ';' and instead saw 'y'.

---

Semicolon insertion is particularly nasty with return. A workaround for this case: don't return multiline statements.

function F(a,b,c)
{
    var toReturn x(a,b,c) +
           y(a,b,c) + 
           z(a,b,c);

    return toReturn;
}

---

Integrate JSLint into your build, and fail builds when you detect

Problem at line 7 character 12: Unreachable 'y' after 'return'. Make this generic for line and character, of course. What you're really looking for is "Unreachable after return".