how do I write a `is_a_last_of_b(a, b)` to check whether `a` is the last child of `b`

Question

a = $('div:first');
b = $('div');

b may contain multiple DOM elements.

But a only contains 1 element.

How do I know if a is the last element of b?

I tried a == $('div:last'),but it's wrong after my test.

And if a is an element of b, how do I get the sibling of a within b?

Clarify

the problem is how I can write a is_a_last_of_b(a, b) to check whether a is the last child of b.

And if a is a direct child of b,how to write next_sibling(a) to return the next sibling of a(only one)?

Your question is really unclear. What is "last element of `b`"? And which sibling are you referring to? — BoltClock, Sep 27 '11 at 06:05
Assuming "element of" means "child of" (your question is still confusing), `div:first` can **never** be a child of another `div` since `div:first` would select the very first, outermost `div` in the document. — BoltClock, Sep 27 '11 at 06:17
@BoltClock,that's just an example ,the problem is how I can write a `is_a_last_of_b(a, b)`. — new_perl, Sep 27 '11 at 06:18
Tried to fix your title, edit if this is not correct. Anything is better than "Question about jQuery" though, can't get much more vague than that. I don't get `is_a_last`, how many **last** elements do you expect? — Wesley Murch, Sep 27 '11 at 06:21
@Wesley Murch ,I know how to select the last ,just put `:last` in the selector. — new_perl, Sep 27 '11 at 06:24

score 1 · Answer 1 · answered Sep 27 '11 at 06:11

1

Can try this

var elements = $("div");
var lastElement = elements.filter(":last");
var firstElement = elements.filter(":first");

For sibling check this out jquery siblings

answered Sep 27 '11 at 06:11

Wazy

score 0 · Answer 2 · answered Sep 27 '11 at 06:10

0

answered Sep 27 '11 at 06:10

Ya Zhuang

How do you get the next **1** sibling of `a`?I only want to get one,not all. – new_perl Sep 27 '11 at 06:11
1

@new_perl: The last child cannot possibly have a next sibling. – BoltClock Sep 27 '11 at 06:12
Yes, in that case,should match nothing.But if not the last,should return the next sibling. – new_perl Sep 27 '11 at 06:13

score 0 · Answer 3 · edited May 23 '17 at 11:55

0

Ok, to compare jquery objects, you can look at some other questions on SO like this one: jQuery object equality

Essentially, in your case where you only want to check for one item you could do this:

var a = $("div:first"),
    b = $("div");

if (b[b.length - 1] === a[0]) {}

// or

if (b.last()[0] = a[0]) {}

Then, to get the next sibling of an element:

b = b.next();

edited May 23 '17 at 11:55

Community

answered Sep 27 '11 at 06:55

nickf

3 Answers3