How to replace repeated words in a text with a reg expression?

Question

JavaScript

How to replace repeated words in text with regular expression?
Found a code that removes duplicate words

var str='При при проверке были были найдены повторяющиеся слова';
alert(str.replace(/([^a-zА-яёЁ]|^)([a-zА-яёЁ]+) (\2)([^a-zA-ZА-яёЁ]|$)/gi,"$1"+"$2"+"$4"))

It is necessary to replace repeated words with the same thing but with formatting.
For example
, replace "at" with
<strong>при</strong>

Answer 1

It is not very clear with the replacement - is it necessary to remove repetitions? If yes:
If not:

str.replace(/([^a-zА-яёЁ]|^)([a-zА-яёЁ]+) (\2)([^a-zA-ZА-яёЁ]|$)/gi, "$1$2 <strong>$3</strong>$4")