html.js

/**
 * @param {TemplateStringsArray} strings
 * @param {...any} values
 * @returns {DocumentFragment}
 */
function html(strings, ...values) {
  let out = ''

  for (let index = 0; index < strings.length; index++) {
    out += strings[index]
    if (index < values.length) {
      const value = values[index]
      out +=
        value == null
          ? ''
          : Array.isArray(value)
            ? value.join('')
            : String(value)
    }
  }

  const template = document.createElement('template')
  template.innerHTML = out.trim()
  return template.content
}