Precautions for jquery traversing checkbox_jquery

When I was working on a front-end project these two days, I wanted to traverse the checkbox on the page through jquery, using the following code:

Copy the code The code is as follows:

var val_instanceCodeStr = "";

$("input[type='checkbox'] [name='chk_jvmMachineName']:checked").each(
function() {
val_instanceCodeStr = "," $(this).val( );
}
);

The variable val_instanceCodeStr is still an empty string at the end, and the function function is not executed;

After checking the information online and comparing it, I found that the code was written correctly. Finally, I found that there was an extra space between [type='checkbox'] [name='chk_jvmMachineName'], which resulted in the checkbox object not being obtained

Jquery multiple selectors cannot be separated by spaces