Riot brings custom tags to all browsers, including IE8. Think React + Polymer but with ejoyable syntax and a small learning curve.

<timer>

  <p>Seconds Elapsed: { time }</p>

  this.time = opts.start || 0

  tick() {
    this.update({ time: ++this.time })
  }

  var timer = setInterval(this.tick, 1000)

  this.on('unmount', function() {
    clearInterval(timer)
  })

</timer>

riot.mount('timer', { start: 0 })

Custom tags lets you build complex views with HTML.

<timetable>
  <timer start="0"></timer>
  <timer start="10"></timer>
  <timer start="20"></timer>
</timetable>

HTML syntax is the de facto language on the web and it's designed for building user interfaces. The syntax is explicit, nesting is inherent to the language and attributes offer a clean way to provide options for custom tags.