Show an random image from a subreddit

subreddits.js

// Place in your body:
// <div id="randomimg"></div>

$(function () {
    GetRandRedditImage("Pics");

    function GetRandRedditImage(subreddit) {
        var imgcontainer = $("#randomimg");
        var aRandomNum = Math.floor((Math.random() * 25) + 1);

        $.getJSON('http://www.reddit.com/r/' + subreddit + '.json?jsonp=?&show=all&limit=25', function (data) {
            $.each(data.data.children, function (i, item) {
                if (i == aRandomNum) {
                    if (item.data.post_hint == "image") {
                        console.log(item.data);
                        imgcontainer.html($("<img>", { src: item.data.url, class: 'imgkeepaspect' }));
                        return false;
                    } else {
                        GetRandRedditImage(subreddit);
                    }
                }
            });
        });
    }
});

It is likely a very strange question, but what is the definition of $ ?

It is likely a very strange question, but what is the definition of $ ?

The dollar sign is commonly used as a shortcut to the function document.getElementById(), and is a function found in many popular libraries in JavaScript. In this case it comes from jQuery, but you could also just implement it yourself by doing something like
function $(x) {return document.getElementById(x);}