js替换字符

Question

var str='test str update Update UPDATE delete Delete DELETE uPdate UPdate';
将以上字符串中的update均用标签包裹，不区分大小写。
期望结果：'test str <b>update</b> <b>Update</b> <b>UPDATE</b> delete Delete DELETE <b>uPdate</b> <b>UPdate</b>';

Answer 1

str = str.replace(/(update)/gi, "<b>$1</b>")

Answer 2