HTML template tag

html.js

'use strict'

/**
 * Print null/undefined and arrays to strings sensibly.
 * @param {*} val
 * @param {String} str
 * @return {String}
 */
function htmlValue(val, str) {
  if (val === null || typeof val === 'undefined') return ''
  if (val instanceof Array) return val.map(htmlValue).join(' ')
  if (typeof val === 'object') return `<pre>${JSON.stringify(val, null, 2)}</pre>`
  return val.toString()
}

/**
 * Template tag function for interpolating variables into HTML templates.
 * @param {String[]} strings
 * @param {...*} values
 * @return {String}
 */
module.exports = function html(strings, ...values) {
  let output = ''
  strings.forEach((str, i) => {
    if (i >= values.length) output += str
    else output += str + htmlValue(values[i], str)
  })
  return output.trim()
}