I want to create a variable based on partial text from a string. The variable will be used in the same test Spec

The element is located thus:

```
 .//*[@id='root']/div[2]/div/div[2]/div/section/div[1]/div[2]/div/h4

```

The output being:

"Your booking reference is: DBM039444."

I need to retrieve DBM039444 or whichever number is generated.

I've tried using the old Excel-type of Left() and Right() but without much success.

Please can anyone offer the correct code