Question

/* get every click event on input tags and send it to foo */
$('input').click( function() {
   foo($(this));
});

function foo(obj) {
/* do something with obj.. */
}

with above code, I will have an input object passed into function foo as an argument obj.
How should I use obj? do I need to re-run selector, like $(obj) to use all jquery-specific methods?

some more question : answers say that I have no need to wrap obj with $() again. what will happen if I re-wrap obj with $(obj)? (suppose function foo can take both jquery-selected objects and non-jquery-selected objects)

Answer 1

You are passing the jQuery object, so no need to wrap $() again.

Did you try running a jQuery function inside the foo function?

$('input').click( function() {
   foo($(this));
});

function foo(obj) {
   console.log(obj.val()); //should print the value in the console.
}

some more question : answers say that I have no need to wrap obj with $() again. what will happen if I re-wrap obj with $(obj)? (suppose function foo can take both jquery-selected objects and non-jquery-selected objects)

You can simply do obj[0] to get the original this object.