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?
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