an example mithril code (with bootstrap CSS classes) for the input component of tags

mithrilTagsInput.js

"use strict"
const m = require("mithril")

// Model
const Tags = {
  list: [],
  add: function(e) {
    if (e.keyCode === 13) {
      Tags.list.push(e.target.value)
      e.target.value = ""
    }
  },
  remove: function(tag) {
    const idx = Tags.list.indexOf(tag)
    if (idx > -1) Tags.list.splice(idx, 1)
  },
}

// View
const TagsInput = {
  view: function() {
    return m(".container", [
      m("input.form-control", {onkeypress: Tags.add}),
      m(".tags", Tags.list.map(function(tag) {
        return [
          m("span.badge.badge-default", [
            tag, " ",
            m("span", {
              onclick: function() {Tags.remove(item)},
            }, m.trust("×")),
            " ",
          ])
        ]
      })
    ])
  },
}

m.mount(document.body, TagsInput)