How to handle A keyNoteFound Exception without Using A try catch Block?

JavaScript

if (prop ["normalcolor"] != null ) { Do Something } I wanna Skip this block of code When it is'nt available in the json. Using the Javascript written i get an error saying KeynotFoundException. I wanna handle this without a try and catch block . Any ideas?. In addition i was able to use this logic in c# and it works.

Json

{ "item":"af-button", "props":{ "label":"Hello1", "highlightedcolor":"#a1d15e", "inverted": "true" }

1 more approach that works with c# But in Javascript It throws the same exception

static function JsonDataContainsKey ( data : JsonData, key : String ) { var result = false; if (data == null) return result; if (!data.IsObject) { return result; } var tdictionary = data as IDictionary; if (tdictionary == null) return result; if (tdictionary.Contains (key)) { result = true; } return result; }