cross-domain.html

<script>
  console.log('<= cross-domain =>')

  const VALUE_KEY = 'myValue'

  window.onload = () => {
    console.log('cross-domain load =>')

    try {
      if (typeof window !== 'undefined' && typeof localStorage !== 'undefined') {
        const currentCartToken = localStorage.getItem(VALUE_KEY)

        if (currentCartToken) {
          window.parent.postMessage(currentCartToken, '*')
        }
      }
    } catch (error) {
      console.error(`Failed to get value in localStorage: ${error}`)
    }
  }

  window.addEventListener('message', ({ data }) => {
    console.log('cross-domain event =>', data)

    try {
      if (typeof window !== 'undefined' && typeof localStorage !== 'undefined') {
        localStorage.setItem(VALUE_KEY, data)
      }
    } catch (error) {
      console.error(`Failed to set value in localStorage: ${error}`)
    }
  })
</script>