Question

In writing a javascript function to evaluate a multi-variate condition, I came across what seems like a parser error in Javascript. Please let me know if I’m forgetting something, or if this is appropriate behavior.

In my function, I’m returning the AND result of several variables, like so:

return
// a comment, for kicks
a1 && a2
&&
b1 && b2
&&
// another comment
c1 && c2
&&
d1 && d2
;

However, even when all of those variables have an explicit value of true, the function is returning undefined instead of the expected true.

I’ve tried several variations of returning this expression, and I’ve found:

1. multiline expression — fails
2. expression on single line — works
3. wrapping expression in paretheses — works
4. setting multiline expression to variable, then returning variable — works

See working examples: http://jsfiddle.net/drzaus/38DgX/

Can anybody explain why this happens?

Answer 1

This is correct behavior. Putting return; in a function will cause it to return undefined. In your example, the line break after return makes the parser think this is the end of the statement, so it returns undefined.