JSFiddle - React, Tailwind, and code Playground

JavaScript

var splitUp = ["this", "is", "a!", "test."];
      var punctuation = [".","!","?"];
      firstCapitalize(splitUp);
      function firstCapitalize(splitUp) {
					var translationString = String(splitUp);
					console.log("translationString before the loop: " + translationString);
					for (var iii = 0; iii < translationString.length; iii++) { 
						if (punctuation.indexOf(translationString[iii]) != -1) {
							console.log(iii+ ": " +translationString[iii]);
							console.log("iii is on: " + iii);
							iii + 2;
							console.log("after increment, iii is on: " + iii);
							translationString[iii].toUpperCase();
						}
					}
					console.log(translationString);
					}