JSFiddle - React, Tailwind, and code Playground

JavaScript

var test1 = 'test1';
var test2 = 'test2';

function checkVariable(variableNameList) {
	for (var iterator = 0; iterator < variableNameList.length; iterator++) {
		var variableName = variableNameList[iterator];
		if (typeof window[variableName] === 'undefined') {
			alert('Variable ' + variableName + ' is not defined');
		} else {
			alert('Variable ' + variableName + ' is defined');			
		}
	}
}

checkVariable(['test1', 'test2', 'test3']);