Regex to remove comments from SQL Query String using JavaScript

Question

I managed to find the regex for handling /* */ cases but it doesn't work well for -- cases. How can I change my regex to fix this?

var s = `SELECT * FROM TABLE_A
/* first line of comment
   second line of comment */
   -- remove this comment too
   SELECT * FROM TABLE_B`;

var stringWithoutComments = s.replace(/(\/\*[^*]*\*\/)|(\/\/[^*]*)|(--[^*]*)/g, '');
/*
Expected:

SELECT * FROM TABLE_A
SELECT * FROM TABLE_B
*/
console.log(stringWithoutComments);

Thank you

https://jsfiddle.net/8fuz7sxd/1/

And what about a comment appearing inside a string literal? And other edge cases. You should really use an SQL parser for this, skip all the comments and then write back the resulting SQL. And what about OR/* comment */DER? — Roland Illig
– Roland Illig, Commented Sep 6, 2019 at 0:20
Remember: whenever you ask for a regex, a regex is usually not the correct solution. — Roland Illig
– Roland Illig, Commented Sep 6, 2019 at 0:21

ManUtopiK · Accepted Answer · 2019-09-06 00:29:23Z

5

var s = `SELECT * FROM TABLE_A
/* first line of comment
   second line of comment */
   -- remove this comment too
   SELECT * FROM TABLE_B`;

var stringWithoutComments = s.replace(/(\/\*[^*]*\*\/)|(\/\/[^*]*)|(--[^.].*)/gm, '');
/*
Expected:

SELECT * FROM TABLE_A
SELECT * FROM TABLE_B
*/
console.log(stringWithoutComments);

// without linebreak
stringWithoutComments = stringWithoutComments.replace(/^\s*\n/gm, "")
console.log(stringWithoutComments);


// without whitespace
stringWithoutComments = stringWithoutComments.replace(/^\s+/gm, "")
console.log(stringWithoutComments);

edited Sep 6, 2019 at 0:29

answered Sep 6, 2019 at 0:18

ManUtopiK

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2 Comments

Alexander Wu Over a year ago

This does not work if the comment contains "*" in it.

Oliver Bock Over a year ago

This will break when /* or -- appear in strings.

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