Making sure a textfield contains a specific string
I have a text field that needs to contain a string, for example:
The user must paste in a youtube share link like this:
I want to validate that whatever they paste in actually contains this:
But is not limited to anything after the backslash.
In a nutshell i just want to make sure that what they have added is actually a youtube share link.
Any idea would be greatly appereciated.