check if html attribute exist and has right value with jquery

Question

Is there a better way for checking an attribute for:

it exist. so value must be false if attribute doesn't exist
Value is correct (boolean)

var isOwner = false;
    if ($(selectedItem).is('[data-isOwner="True"]') || $(selectedItem).is('[data-isOwner="true"]')) {
        isOwner = true;
    } else {
        isOwner = false;
    }

Now I need to check for 'True' and 'true'...

Thanks

Filip Roséen · Accepted Answer · 2012-07-13 11:45:45Z

3

You can convert the value stored in data-isOwner to lower case and only compare the value to 'true'.

if (($(selectedItem).attr ('data-isOwner') || '').toLowerCase () == 'true')

The above use of <wanted-value> || '' will make it so that if the selectedItem doesn't have the attribute data-isOwner the expression will result in an empty string, on which you can call toLowerCase without errors.

Without this little hack you'd have to manually check so that the attribute is indeed present, otherwise you'd run into a runtime-error when trying to call toLowerCase on an undefined object.

If you find the previously mentioned solution confusing you could use something as

var attr_value = $(selectedItem).attr ('data-isOwner');

if (typeof(attr_value) == 'string' && attr_value.toLowerCase () == 'true') {
  ...
}

edited Jul 13, 2012 at 11:45

answered Jul 13, 2012 at 11:37

Filip Roséen

64.2k20 gold badges153 silver badges201 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

LockTar Over a year ago

I like your approache. Can it also be checked typesafe? I set the property with ASP .NET MVC4 and C# so it is a boolean. Should I parse the lowercase to a boolean? and then compare with: === true?

index Over a year ago

I think every values always comes out at string unless you parse it into something in your JS.

Filip Roséen Over a year ago

@LockTar if you store a value inside an element's attribute it will be of type string when using $(selector).attr (key) or the equivalent, if you want it to be handled differently you'll need to provide your own wrapper around the getter.

LockTar Over a year ago

Thanks. it worked. I only used === because it should be saver then == 'true'

Collectives™ on Stack Overflow

check if html attribute exist and has right value with jquery

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related