moodle/lib/form/url.js

M.form_url = {};

M.form_url.init = function(Y, options) {
    options.formcallback = M.form_url.callback;
    if (!M.core_filepicker.instances[options.client_id]) {
        M.core_filepicker.init(Y, options);
    }
    Y.on('click', function(e, client_id) {
        e.preventDefault();
        M.core_filepicker.instances[client_id].show();
    }, '#filepicker-button-'+options.client_id, null, options.client_id);

};

M.form_url.callback = function (params) {
    document.getElementById('id_externalurl').value = params.url;
};