JQuery - how do i detect how many divs of a given class exist within a given div?

问题

I have a div like this:

<div id="x" name="x" class="x" style=""></div>

and contained within this div I have several divs like this:

<div id="y_1" name="y_1" class="y" style=""></div>
<div id="y_2" name="y_2" class="y" style=""></div>
<div id="y_3" name="y_3" class="y" style=""></div>

etc.

QUESTION 1: How do I detect how many of these divs (class="y") are contained within the container div (class="x")? - (just an alert("") with the number, for example).

QUESTION 2: How do I do something to each of these y-divs (class="y") such as a function that might place the letter "Y" into all of the y-divs using $('.y').html("Y"); , for example??

Any help appreciated guys....

回答1:

You need to find the elements within the ancestor element.

$('#x div.y').length; // number of class y elements under element x
$('#x div.y').html('Y'); // run a jQuery method on the y elements

See the API:

• descendant selector
• length property

回答2:

alert($('.x .y').length);

$('.x .y').html('Y');

回答3:

//instead of $('#x .y') you can also use $('#x').find('.y')
alert($('#x .y').length())

$('#x .y').each(function(){
    //do what you want to $(this)
    $(this).html('Y');
});

回答4:

Try this.

alert($('.x .y').length)

http://api.jquery.com/length/

回答5:

1. The length() method gets the total amount of returned elements:

alert($('.x .y').length());

2. You were correct in how to set the content on all of the returned elements:

$('.x .y').html('Y');

来源：https://stackoverflow.com/questions/6243554/jquery-how-do-i-detect-how-many-divs-of-a-given-class-exist-within-a-given-div