Util function to combine classNames conditionally

JoinClassNames.ts

function join(
  ...classNames: ([boolean, string] | string | undefined | null)[]
) {
  let result = "";
  for (let x = 0; x < classNames.length; x++) {
    const value = classNames[x];
    if (!value) continue;
    if (typeof value === "string") {
      result += " " + value;
      continue;
    }
    if (value[0]) result += " " + value[1];
  }
  return result;
}