jQuery's way of asserting an element with a certain ID exist in the page?

Question

I was going to do $("#foo") !== null to assert that an element with the id="foo" does exist in the page, but it turns out even if the element doesn't exist, the selector $("#foo") still returns an object.

So to test whether the selector can find an element, should

assert($("#foo").length >= 1);

be used? I also thought of using assert($("#foo").is("div") but if the HTML is changed, and the element is not a div but becomes a p or span, then it will break the assert. What is a good, standard way to assert that the element does exist?

jsfiddle sample: http://jsfiddle.net/qnbAn/1/

Just `if ( $("#foo").length )` should do ! – adeneo Apr 01 '13 at 08:02 — adeneo, Apr 01 '13 at 08:02

score 1 · Answer 1 · answered Apr 01 '13 at 08:03

1

Why not just:

if ($("#foo").length){
    // element with id foo existed
}

Since id of an element is unique.

answered Apr 01 '13 at 08:03

Eli

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Your first conditional expression is always `true` even if `#foo` matches nothing. jQuery objects are objects, and objects are always `true` in a boolean context. – Frédéric Hamidi Apr 01 '13 at 08:04
@FrédéricHamidi true , fixed :) – Eli Apr 01 '13 at 08:05

score 0 · Answer 2 · answered Apr 01 '13 at 08:01

0

Yes, you should use length to check if a given selector matches anything.

Selectors that match nothing result in empty jQuery objects, but even empty jQuery objects are valid instances and evaluate to true in a boolean context.

answered Apr 01 '13 at 08:01

Frédéric Hamidi

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score 0 · Answer 3 · edited May 23 '17 at 12:28

0

Use

$('#elementId').Length > 0

like

Is there an "exists" function for jQuery?

edited May 23 '17 at 12:28

Community

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answered Apr 01 '13 at 08:04

Saeed Afshari

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score 0 · Answer 4 · answered Apr 01 '13 at 08:13

0

Do this in simple like this

if($("#mydiv").length){
 // mydiv exist
}

answered Apr 01 '13 at 08:13

rajesh kakawat

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jQuery's way of asserting an element with a certain ID exist in the page?

4 Answers4