Regex working in JS but not in a tester?

Regex working in JS but not in a tester?
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#1

A friend made me a Regex for my calculator (/^0+\B/, “”) which stops the user from inputting 00. I´m new to Regex and I´m trying to understand them. However, when I enter the regex here:


It doesn´t seem to match 00. So what´s going on?


#2

I believe you need to enter only the part between forward slashes (/) to check it on regex101