I am trying to create a regex for a list of accepted symbols and character string

Question

I am building a test function that should only accept the following:
-
*
+
.
,
$
9
Z
V
B
CR - only once not with DB
DB - only once not with CR
I have gotten the first few to work like so: new RegExp(/^([-*+.,$9ZVB]|CR|DB)*$/gm), but I annot get the regex to only allow the CR or DB to appear only once either at beginning or end of the string.  Any suggestions?
Test at https://regex101.com/r/1qT86R/2

Toto · Answer

I'm guessing you are using javascript.
You can use the regex:
^(?:(?:CR|DB)[-*+.,$9ZVB]+|[-*+.,$9ZVB]+(?:CR|DB))$

Demo & explanation


var test = [
    '$---,---,--9.99BCR',
    '$---,---,--9.99BDB',
    'CR$---,---,--9.99B',
    'DB$---,---,--9.99B',
    'CR$---,---,--9.99BCR',
    'CR$---,---,--9.99BDB',
];
console.log(test.map(function (a) {
  return a+' : '+/^(?:(?:CR|DB)[-*+.,$9ZVB]+|[-*+.,$9ZVB]+(?:CR|DB))$/.test(a);
}));

Ilya Lysenko · Answer

Try this expression:
^(CR|DB)[-*+.,$9ZVB]+$|^[-*+.,$9ZVB]+(CR|DB)$

or
^((CR|DB)[-*+.,$9ZVB]+|[-*+.,$9ZVB]+(CR|DB))$

You can test it here: https://regexr.com/58tf1

I am trying to create a regex for a list of accepted symbols and character string

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