One click REV balance from the browser

REV_balance_chrome_bookmark.html

data:text/html,<script>
const revBalance = addr => `
  new return, rl(\`rho:registry:lookup\`), RevVaultCh, vaultCh in {
    rl!(\`rho:rchain:revVault\`, *RevVaultCh) |
    for (@(_, RevVault) <- RevVaultCh) {
      @RevVault!("findOrCreate", "${addr}", *vaultCh) |
      for (@maybeVault <- vaultCh) {
        match maybeVault {
          (true, vault) => @vault!("balance", *return)
          (false, err)  => return!(err)
        }
      }
    }
  }
`
const url = 'http://104.197.246.182:40403/api/explore-deploy'
const addr = prompt('Please enter REV address', '<REV address>')
const req = {method: 'POST', body: revBalance(addr)}
const render = msg => document.body.innerHTML = `<h1>${msg}</h1>`
const readRes = ({expr: [r]}) => {
  console.log("Result", r)
  const bal = r.ExprInt && r.ExprInt.data
  const err = r.ExprString && r.ExprString.data
  return typeof bal === 'number' ? `Balance: ${bal * 10e-9}` : `ERROR: ${err}`
}
fetch(url, req).then(r => r.json())
  .then(readRes).then(render).catch(render)
</script>

@jimscarver I'm not sure. Chrome supports JS with const definition. You can try replacing const with let or var constructs.