From the Docs:
(function( $ ){
$.fn.myfunction = function() {
alert(‘hello world’);
return this;
};
})( jQuery );
Then you do
$(‘#my_div’).myfunction();
In spite of all the answers you already received, it is worth noting that you do not need to write a plugin to use jQuery in a function. Certainly if it’s a simple, one-time function, I believe writing a plugin is overkill. It could be done much more easily by just passing the selector to the function as a parameter. Your code would look something like this:
function myFunction($param) {
$param.hide(); // or whatever you want to do
…
}
myFunction($(‘#my_div’));
Note that the $ in the variable name $param is not required. It is just a habit of mine to make it easy to remember that that variable contains a jQuery selector. You could just use param as well.