extract variables from an expression using javascript regexp

Question

For example, here is a string representing an expression:

var str = 'total = sum(price * qty) * 1.09875';

I want to extract variables (i.e., 'total', 'price' and 'qty' but not 'sum' since 'sum' is a function name) from this expression. What is the regexp pattern in javascript? Variable name consists of letters, digits, or the underscore, beginning with letters or the underscore.

it's easy to write one for this specific case, but very very hard to write a generalized version. — Anurag
– Anurag, Commented Apr 9, 2010 at 19:37

kennytm · Accepted Answer · 2010-04-09 19:33:54Z

4

return "total = sum(price * qty) * 1.09875".match(/[a-z_]\w*(?!\w*\s*\()/ig);

Here,

[a-z_] matches 1 letter or 1 underscore,
\w* matches 0 or more letters, digits or underscore (\w means [a-zA-Z0-9_])
(?!…) is a negative lookahead. The match will fail if the stuff inside is matched.
\w*\s*\( matches some letters, followed by some spaces, and then an (. This allows function names to be rejected.

answered Apr 9, 2010 at 19:33

kennytm

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