let person = "Mike"
let age = 28

function myTag(strings, personExp, ageExp) {
  let str0 = strings[0] // "That "
  let str1 = strings[1] // " is a "

  // There is technically a string after
  // the final expression (in our example),
  // but it is empty (""), so disregard.
  // let str2 = strings[2];

  let ageStr
  if (ageExp > 99) {
    ageStr = "centenarian"
  } else {
    ageStr = "youngster"
  }

  // We can even return a string built using a template literal
  return `${str0}${personExp}${str1}${ageStr}`
}

let output = myTag`That ${person} is a ${age}`

console.log(output)
// That Mike is a youngster