delay promises

delay_request_promises.js

function requestAllWithDelay (urls, delay) {
  return urls.reduce((promise, url) => {
    return promise
      .then((responses) => {
        return fetch(url) // Or whatever request library you're using. If it doesn't support promises, you can wrap it in `new Promise((resolve, reject) => someLib(url, { onSuccess: resolve, onError: reject }));` or something similar.
          .then(response => {
            return new Promise(resolve => {
              setTimeout(resolve, delay, responses.concat(response)); // replies.concat might not work, depending on how you want to accumulate all the data. Maybe you don't even care about the responses?
            })
          })
      })

  }, Promise.resolve([]))
}

requestAllWithDelay(['http://...', ...], 1000)
  .then(allResponsesInAnOrderedArray => { ... })