Check existence of an attribute with JQuery

Question

I have a colection of checkboxes with generated ids and for a reason, some have an extra attribute. Is possible using JQuery to check if an element has a specific attribut ? For example can I verify if the following element has as attribute "myattr" ? The value of the attribute can vary.

<input type="checkbox" id="A" myattr="val_attr">A</input>

Thank you for all the responses. For example how can I get a collection of all checkboxes that have this attribute without checking one by one ? Is possible ?

Answer 1

if ($('#A').attr('myattr')) {
    // attribute exists
} else {
    // attribute does not exist
}

EDIT:

The above will fall into the else-branch when myattr exists but is an empty string or "0". If that's a problem you should explicitly test on undefined:

if ($('#A').attr('myattr') !== undefined) {
    // attribute exists
} else {
    // attribute does not exist
}

Answer 2

Do you mean can you select them? If so, then yes:

$(":checkbox[myattr]")

Answer 3

$("input#A").attr("myattr") == null

Answer 4

In JavaScript,...

null == undefined

...returns true*. It's the difference between == and ===. Also, the name undefined can be defined (it's not a keyword like null is) so you're better off checking some other way. The most reliable way is probably to compare the return value of the typeof operator.

typeof o == "undefined"

Nevertheless, comparing to null should work in this case.

* Assuming undefined is in fact undefined.

Answer 5

http://stackoverflow.com/questions/1318076/jquery-hasattr-checking-to-see-if-there-is-an-attribute-on-an-element