Check if a check box is checked or not (js/jquery)

Question

I want to check if a certain check box is selected using JavaScript/jQuery.

Here is the code I tried:

var a;
    if ($("#add_desc").checked == 1){
        a = "true";
    }else{
        a= "false";
    }

I have also tried:

var a;
    if ($("#add_desc").checked){
        a= "true";
    }else{
        a= "false";
    }

It always returns false once I alert the variable a .

Any idea why it won't work for me? Am I doing it wrong?

Thanks!

Answer 1

To get the value of the checked property on a checkbox input, use the .prop() method, or get the value directly from the DOM element. [0] returns the first selected DOM element.

var a;
if ($("#add_desc")[0].checked){
    a= "true";
}else{
    a= "false";
}

or

var a;
if ($("#add_desc").prop("checked")){
    a= "true";
}else{
    a= "false";
}

Edit
For versions of jQuery older than 1.6, .prop didn't exist, use .attr as a direct replacement.

Answer 2

简单，

var a = $('#element:checkbox').is(':checked');

Answer 3

The "jQuery way" would be to use .is(":checked") :

var a;
if ($("#add_desc").is(":checked")){ // box is checked
    a = "true";
} else{ // box is not checked
    a= "false";
}

I use this a lot in my web apps and it works perfectly.

From the jQuery .is documentation page :

Unlike other filtering methods, .is() does not create a new jQuery object. Instead, it allows you to test the contents of a jQuery object without modification. This is often useful inside callbacks, such as event handlers.

Answer 4

javascript中的三元运算符与jQuery .is（）相结合是最短的解决方案。

var a = ($("#add_desc").is(":checked")) ? "true" : "false";

Answer 5

try:

if ($('#add_desc').is(':checked')) {
  a = "true";
} else {
  b = "false";
}

you may also not want to use strings, ie use true and false instead of "true" and "false"

Answer 6

Try

$get("#add_desc").checked == true

Also

$("#add_desc").prop("checked", true);
$("#add_desc").prop("checked", false);