如何不使用每个而访问复选框数组的第一个元素？

Question

I have a Jquery event that will collect the list of selected checkboxes and I am currently experimenting their behaviours by trying to access them 1 by 1.

$('#sub').click(function () {

    var cb = $("input[type='checkbox']:checked");
    var count = cb.length;

    alert(cb[0].prop('checked'));

    if (count == 0) {
        alert('No subjects selected');
        return false;
    } else {
        return confirm(count + " row(s) selected, proceed?");
    }
});

Accessing cb directly won't work for some reason.

I need to do something like this :

 cb.each(function (i) {
    alert($(this).prop('checked'));
});

But this will require me to loop through all of them when I only need the first element of the array, to see if it's true.

Are there any methods and can someone tell me why my first approach didn't work? I tried using for loop but no luck.

Answer 1

You can use eq()

alert(cb.eq(0).prop('checked'));

or cb[0] will return dom object

alert(cb[0].checked);

Ref : https://learn.jquery.com/using-jquery-core/faq/how-do-i-pull-a-native-dom-element-from-a-jquery-object/

Answer 2

What you are trying to do is to check whether at least one item is selected, since cb has only checked items you can just check whether the set has atleast one item like

$('#sub').click(function () {
    var cb = $("input[type='checkbox']:checked");

    if (!cb.length) {
        alert('No subjects selected');
        return false;
    } else {
        return confirm(count + " row(s) selected, proceed?");
    }

Answer 3

This:

var cb = $("input[type='checkbox']:checked");

Doesn't return a single element, it potentially returns many.

This will target the first checked checkbox:

var cb = $("input[type='checkbox']:checked:first");

This will target the first checkbox regardless of state:

var cb = $("input[type='checkbox']:first");