iD/js/lib/d3.jsonp.js

d3.jsonp = function (url, callback) {

    function rand() {
        var chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz',
            c = '', i = -1;
        while (++i < 15) c += chars.charAt(Math.floor(Math.random() * 52));
        return c;
    }

    function create(url) {
        var e = url.match(/callback=d3.jsonp.(\w+)/),
            c = e ? e[1] : rand();
        d3.jsonp[c] = function(data) {
            callback(data);
            delete d3.jsonp[c];
            script.remove();
        };
        return 'd3.jsonp.' + c;
    }

    var cb = create(url),
        script = d3.select('head')
        .append('script')
        .attr('type', 'text/javascript')
        .attr('src', url.replace(/({|%7B)callback({|%7D)/, cb));

};