I would like some help in building a regular expression. The conditions are as follows

• The expression must start with #
• Then it should contain atleast one or more groups of alphanumeric characters separated by -
• Each group contains atleast one alphanumeric character
• The expression should end either with -apples or -bananas

Some test cases

1. #hshg1h2-hd212df-7632jhsd-bananas (Match)
2. #jhkj31j-jkh213j-jjkhjj324-apples (Match)
3. hjsdjjhsd-jhsshdjs-jdshdsj-apples (No Match)
4. #---apples (No Match)
5. #jhkj31j-jkh213j-jjkhjj324 (No Match)
6. #jhkj31j-jkh213j-jjkhjj324-apples-bananas (No Match)

I created the following expression ^#([a-zA-Z0-9]{1,}-){1,}(apples|bananas)$. For most of the test cases, it provides the correct result. However it also matches the test case 6 which it should not.

Background

The test cases simulate product-ids for the two products apples and bananas. Those ids always contains as the last group -bananas or -apples. Thus -apples-bananas or vice versa is suppose be invalid product id.

Could anyone please show me how can I do this?

CodePudding user response：

You can use lookaheads and alteration:

/^#(?!.*apples.*bananas|.*bananas.*apples)(?=[a-zA-Z0-9] -[a-zA-Z0-9] ).*(?:apples|bananas)$/

Demo

And it is always good to use word boundary assertions:

/^#(?!.*\bapples\b.*\bbananas\b|.*\bbananas\b.*\bapples\b)(?=[a-zA-Z0-9] -[a-zA-Z0-9] ).*(?:\bapples\b|\bbananas\b)$/