TypeScript

HTML

<div id="app"></div>

TypeScript

enum SiteCodes {
    'USA',
    'CAN',
    'GB'
}

let badSiteCode = 'badSiteCode';
let validSiteCode = 'USA'
const template = badSiteCode + 'is in SiteCodes? = ' + (badSiteCode in SiteCodes) + '<br/>' + 'validSiteCode is in SiteCodes? = ' + (validSiteCode in SiteCodes);

document.querySelector("#app").innerHTML = template;