Error: Syntax error, unrecognized expression: # jquery

Question

I have the following code:

$('.questionAlternative').change(function() {
    var nestedQuestion = $(this).attr('nestedQuestion');
    if(nestedQuestion != null || nestedQuestion != "") {
        $("#"+nestedQuestion).show();
    } else {
        $(this).parent().next('.nestedQuestionContainer').hide();
    }
}

The .questionAlternative is two radiobuttons, yes or no.

When I change to No, I get the following error:

Error: Syntax error, unrecognized expression: #
throw new Error( "Syntax error, unrecognized expression: " + msg );

I can't understand why. If nestedQuestion is empty, It should not go into the If-statement. But It seems like It doing It anyway?

"" != null is true

Andreas
– Andreas

2016-10-31 14:52:39 +00:00
Commented Oct 31, 2016 at 14:52 — Andreas
– Andreas, Commented Oct 31, 2016 at 14:52

T.J. Crowder · Accepted Answer · 2016-10-31 14:54:39Z

6

Your condition is wrong. It says "if nestedQuestion is not null OR nestedQuestion is not ""..." But "" is not null, so that condition is true for "".

Change it to and (&&):

if(nestedQuestion != null && nestedQuestion != "") {

or just use the fact that both null and "" are falsy:

if(nestedQuestion) {

..and actually, attr will never give you null anyway. It will only give you a string (possibly "") or undefined. (But undefined == null is true, so...)

edited Oct 31, 2016 at 14:54

answered Oct 31, 2016 at 14:53

T.J. Crowder

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2 Comments

Bryan Over a year ago

Ah, did not know that "" was not null. Thank you.

T.J. Crowder Over a year ago

@Bryan: :-) It's one of those things, they're both falsy, but they're not == to each other.

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