evaluate `resin(x)` function in string with regular expression

I am trying to evaluate a function in a string like this resin(8)

so if i have this text 3*(resin(4)-sin(12))

I need to evaluate resin(1) so it will replace that while occurrence with the result which should look like 392.9

I am using this

result = result.replace(/(?<={resin\()(.*?)(?=\)})/, x => parseInt(392.9 * x))

but i need it to replace the resin( part and the ) closing parentheses.

is there any regexp magic I can use?

>Solution :

Are you sure you need a positive lookbehind and a positive lookahead?

In my opinion, when using a regex replacer, as you did, the grouping is more than enough to accomplish the task:

result = result.replace(/resin\((\d+\.?\d*)\)/g, (_, x) => parseInt(392.9 * parseFloat(x)))

Edit:
I just read in your question that you need resin(1) to be replaced with 392.9, but in your snippet you used parseInt and I kept it in my example. Just drop the parseInt in case you don’t need the result to be an integer