How is "eval()" harmful?

[KB15]

I was using a reference from SNGuru and found that the code they provided comes up as a warning:

https://www.servicenowguru.com/system-ui/adding-fields-service-catalog-checkout-screen/

What would be the downsides and is there a better way to code this?

[TrevorK · Accepted solution]

I could try and explain why many people do not like eval() and some of the downsides, but there are many others who do a better job of explaining it than I do:

https://www.nczonline.net/blog/2013/06/25/eval-isnt-evil-just-misunderstood/

How evil is eval? — JavaScript, JavaScript…

Tommy Hodgins's response to Why is using `eval` considered bad in JavaScript? - Hashnode

There are many other links, but that should hopefully give you some background information on eval() because there is some contention to its use.