Show lat/lng of mouse cursor in #iD

latlng.js

id.surface().on('mousemove.custom', function() {
    function wrap(x, min, max) { var d = max - min; return ((x - min) % d + d) % d + min; }

    var ll = d3.select('#content')
        .selectAll('#latLng')
        .data([0]);

    ll.enter()
        .append('div')
        .attr('id', 'latLng')
        .attr('class', 'fillD')
        .attr('style', 'position:absolute; top:70px; right:80px; padding:5px; color: #ccc');

    ll
        .text(function() {
            var coord = id.map().mouseCoordinates();
            return wrap(coord[1], -90, 90).toFixed(5) + ', ' + wrap(coord[0], -180, 180).toFixed(5);
        });

});

I am new to the D3 Frame work. Can U please suggest me where to include this code in my iD.js .