How to use the mutant.Value function in mutant

function app () {
    process.nextTick(() => insertCss(api.styles()))

    var view = Value(getView())
    var screen = h('App', view)

    window.onhashchange = () => view.set(getView())
    document.body.appendChild(screen)

    // tabs (another core module) currently handles this
    // window.addEventListener('error', window.onError = displayError)

    return screen
  }

function PreviewSetup (strings) {
      var showPreview = Value(false)
      var previewBtn = h('Button',
        {
          className: when(showPreview, '-strong', '-subtle'),
          'ev-click': () => showPreview.set(!showPreview())
        },
        when(showPreview, strings.blogNew.actions.edit, strings.blogNew.actions.preview)
      )
      return { previewBtn, showPreview }
    }
    var { previewBtn, showPreview } = PreviewSetup(strings)

return nest('app.html.lightbox', (content, isOpen) => {

    if (typeof isOpen !== 'function') isOpen = Value(false)

    const closeMe = () => isOpen.set(false)


    const lb = h('Lightbox', { className: when(isOpen, '-open', '-close'), 'ev-click': closeMe },
      h('div.content', {'ev-click': (ev) => ev.stopPropagation()},[
        content
      ]))

    lb.close = closeMe

    return lb
  })
}

function menu (handleClick) {
    var state = Value('')

    return h('Menu', {
      classList: [ state ],
      'ev-mouseover': () => state.set('-active'),
      'ev-mouseout': () => state.set('')
    }, [
      h('div', api.app.html.menuItem(handleClick))
    ])
  }
}