Set modules.

src/bootstrap/Button.js

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2019 CZ.NIC z.s.p.o. (http://www.nic.cz/)
+ *
+ * This is free software, licensed under the GNU General Public License v3.
+ * See /LICENSE for more information.
+ */
+
+import React from 'react';
+import PropTypes from 'prop-types';
+
+const OFFSET = 8;
+const SIZE = 3;
+const SIZE_CLASS = ' offset-lg-' + OFFSET + ' col-lg-' + SIZE;
+const SIZE_CLASS_SM = ' col-sm-12';
+
+Button.propTypes = {
+    /** Additional class name. */
+    className: PropTypes.string,
+    /** Use foris form size and offset. */
+    forisFormSize: PropTypes.bool,
+    /** Show loading icon. */
+    loading: PropTypes.bool,
+    /** Button content. */
+    children: PropTypes.oneOfType([
+        PropTypes.string,
+        PropTypes.element,
+        PropTypes.node,
+        PropTypes.arrayOf(PropTypes.node),
+    ]).isRequired
+};
+
+export function Button({className, loading, forisFormSize, children, ...props}) {
+    className = className ? 'btn ' + className : 'btn btn-primary ';
+    if (forisFormSize)
+        className += SIZE_CLASS + SIZE_CLASS_SM;
+
+    const span = loading ?
+        <span className='spinner-border spinner-border-sm' role='status' aria-hidden='true'/> : null;
+
+    return <button className={className} {...props}>
+        {span} {span ? ' ' : null} {children}
+    </button>;
+}