I use this script on my old Blogger (https://tinkeringetc.blogspot.com) to redirect to my Medium (https://medium.com/my-life-as-a-tinkerer/)

redirection.html

<!--
Code Flow:
* Checks page-title aginst all pages/posts

* Calls checkCookie()
  * uses getCookie() to get cookie
  * True: redirectPage(link);
  * False: askToRedirect(link, post, false);
  * Doesn't exist: askToRedirect(link, post, true);

  * askToRedirect()
    * puts text on screen/ in popup
    * calls storeCookie() with result

  * storeCookie()
    * stores cookie
    * calls redirectPage() if True
-->


<!--
stylize the button - similar to bootstrap's warning button
make it full width
and put a cursor over it so it appears as a link
-->
<style>
.redirectButton {
    display: inline-block;
    width: 100%;
    color: #fff;
    background-color: #f0ad4e;
    border-color: #000;
    font-weight: 400;
    line-height: 1.25;
    text-align: center;
    white-space: nowrap;
    vertical-align: middle;
    padding: .5rem 1rem;
    font-size: 1rem;
    border-radius: .25rem;
    cursor: pointer;
}
</style>

<!-- make an area that I can modify -->
<p id="redirect"></p>

<script>
// the class name for the title so I can see what page I'm on
var post_title = document.getElementsByClassName('post-title entry-title');

// redirect current page to passed link
function redirectPage(link) {
  window.location.assign(link);
};

// store cookie related to redirection
// if true, also redirect page
function storeCookie(link, redirect) {
  // cookie expiration is set as far into the future as unix allows
  // http://stackoverflow.com/a/22479460/7564623
  if (redirect == true) {
    // store cookie as true
    document.cookie = "tinkererredirect=True;expires=Tue, 19 Jan 2038 03:14:07 GMT;path=/";
    // redirect page
    redirectPage(link);
  }
  else {
    // store cookie as false
    document.cookie = "tinkererredirect=False;expires=Tue, 19 Jan 2038 03:14:07 GMT;path=/";
    // stay on page
  }
}

// ask the user if they want to move to Medium
function askToRedirect(link, post, popup) {
  // change text depending if its a post or not
  if (post == true) {
    var text = "I have migrated my blog to Medium.";
  }
  else {
    var text = "I have migrated this page to my personal website.";
  }

  // always add this text
  text = text.concat(" Would you like to redirect there for the best reading experience?");

  // display a confirmation box popup
  if (popup == true) {
    // will pass response into storeCookie()
    var ask = confirm(text);
  }

  // add redirect button after text
  text = text.concat("<br><br><button class='redirectButton'>Redirect page</button>");

  // put the text and button in two places:
  // 1) side bar
  document.getElementById("redirect").innerHTML = text;
  // 2) top bar
  document.getElementsByClassName('description')[0].innerHTML = text;

  // apply click handler to those buttons
  // which will set a cookie and redirect the user to the correct link
  var buttonsClass = document.getElementsByClassName("redirectButton");
  for (var i = 0; i < buttonsClass.length; i++) {
    buttonsClass[i].addEventListener('click', function(){
      storeCookie(link, true);
    });
  }

  // store cookie depending on the result from the confirmation popup
  storeCookie(link, ask);
}

// get cookie from browser
// https://www.w3schools.com/js/js_cookies.asp
function getCookie(cname) {
    var name = cname + "=";
    var decodedCookie = decodeURIComponent(document.cookie);
    var ca = decodedCookie.split(';');
    for(var i = 0; i <ca.length; i++) {
        var c = ca[i];
        while (c.charAt(0) == ' ') {
            c = c.substring(1);
        }
        if (c.indexOf(name) == 0) {
            return c.substring(name.length, c.length);
        }
    }
    return "";
}

// check if custom cookie exists
// and read it's value
// then redirect accordingly
function checkCookie(link, post) {
  var redirect = getCookie("tinkererredirect");

  // redirect page if cookie is True
  if (redirect == "True") {
    redirectPage(link);
  }
  else if (redirect == "False") {
    // otherwise display information on page asking to redirect
    askToRedirect(link, post, false);
  }
  // cookie doesn't exist
  else {
    // display popup for first timers
    askToRedirect(link, post, true);
  }
}

// main code - checks which page based on post_title
// if more than 1, you're on the main page
if (post_title.length != 1) {
  checkCookie("https://medium.com/my-life-as-a-tinkerer/", true);
}
// otherwise, you're on some post
else {
  switch (post_title[0].innerHTML) {
    // this will trigger on the post or the page, but just redirect to page
    // i.e. two things are named this
    case "\nMSP430 Reaction Game\n":
      checkCookie("http://tinkerer.us/projects/msp430-reaction-game.html", false);
      break;
    // this is for the page
    case "\nHomebrew Gameboy Cartridge\n":
      checkCookie("http://tinkerer.us/projects/homebrew-gameboy-cartridge.html", false);
      break;
    // these are the remaining posts
    case "\nHow to Automatically Unzip Files Downloaded from Chrome on Windows\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/how-to-automatically-unzip-files-downloaded-from_chrome-on-windows-354032a4b048", true);
      break;
    case "\nParticle-Losant Integration using Webhooks\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/particle-losant-integration-using-webhooks-eb2aaafb1782", true);
      break;
    case "\nIoT Liquor Lights using Spark Core\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/iot-liquor-lights-using-spark-core-68b46177e808", true);
      break;
    case "\nSpark Lamp Update\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/spark-lamp-update-95e3aa434a54", true);
      break;
    case "\nSpark Lamp\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/spark-lamp-b35217f389cd", true);
      break;
    case "\nelectric imp-Controlled 120VAC Relay Switcher Software Update\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/electric-imp-controlled-120vac-relay-switcher-software-update-8d8d8b5c8bdc", true);
      break;
    case "\n1st 1/4 of '14\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/1st-1-4-of-14-84b59461e587", true);
      break;
    case "\nelectric imp-Controlled 120VAC Relay Switcher\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/electric-imp-controlled-120vac-relay-switcher-6219200ad7ea", true);
      break;
    case "\nPast Few Months\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/past-few-months-de4b20ae22a7", true);
      break;
    case "\nAdjustable RGB LED Color Cube\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/adjustable-rgb-led-color-cube-7573d160d38f", true);
      break;
    case "\nProgramming Arduino Bootloader on ATmega328p with ZeptoProg II\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/programming-arduino-bootloader-on-atmega328p-with-zeptoprog-ii-869515c57a6", true);
      break;
    case "\nCloset Door Lightswitch\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/closet-door-lightswitch-fb3a25d75f9d", true);
      break;
    case "\nWhy I've Been Gone\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/why-ive-been-gone-ca4044598149", true);
      break;
    case "\nGoogle Chrome Remote Webcam Viewer\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/google-chrome-remote-webcam-viewer-4d8f12e9518e", true);
      break;
    case "\nFilament Spool Stand\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/filament-spool-stand-4e296ed34670", true);
      break;
    case "\nMy 3D Prints Summary #1\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/my-3d-prints-summary-1-ab2b12135f7f", true);
      break;
    case "\nPrintrbot Calibration Prints\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/printrbot-calibration-prints-39c8b0f1b2e4", true);
      break;
    case "\nAutomatic Garden Waterer: Part 2\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/automatic-garden-waterer-part-2-b54c2f594541", true);
      break;
    case "\nPrintrbot Tip: Leveling the Printrbed\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/printrbot-tip-leveling-the-printrbed-bf945e115d74", true);
      break;
    case "\nPrintrbot Build: Part 2\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/printrbot-build-part-2-30951248ff7d", true);
      break;
    case "\nPrintrbot Build: Part 1\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/printrbot-build-part-1-3fc1060bdb5", true);
      break;
    case "\nAutomatic Garden Waterer: Part 1\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/automatic-garden-waterer-part-1-9fc4b080df34", true);
      break;
    case "\nFather's Day Phones\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/fathers-day-phones-4af04a87533b", true);
      break;
    case "\nSome More Shelves\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/some-more-shelves-6b9c3c29b1c8", true);
      break;
    case "\nContinuity Checker\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/continuity-checker-4d7f15dc356c", true);
      break;
    case "\nHow (Not) To Fix A Stereo Amplifier\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/how-not-to-fix-a-stereo-amplifier-5c1fc7d86ed6", true);
      break;
    case "\n5V Regulated Breadboard Power Supply\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/5v-regulated-breadboard-power-supply-7edc2d97d110", true);
      break;
    case "\nHomemade Variable Power Supply\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/homemade-variable-power-supply-186ec1b75aa2", true);
      break;
    case "\nMaking LadyAda's MiniPOV3\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/making-ladyadas-minipov3-4dd92b694166", true);
      break;
    case "\nI'm Screwed\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/im-screwed-bb1bb72d2b44", true);
      break;
    case "\nEasy Documentation Organization\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/easy-documentation-organization-ba706a35f0b5", true);
      break;
    case "\nBeautiful iPhone Protection (for Cheap!)\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/beautiful-iphone-protection-for-cheap-1ac4316aa5a", true);
      break;
    case "\nI'm Back!\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/im-back-d2161426fbf8", true);
      break;
    case "\nBus Pirate v4 Assembly\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/bus-pirate-v4-assembly-d55eb5b1d716", true);
      break;
    case "\nStorage Container Shelving System\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/storage-container-shelving-system-43c601c46bd9", true);
      break;
    case "\nCrater Lake National Park\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/crater-lake-national-park-1204b79e6cdd", true);
      break;
    case "\nGoogle Calendar/Contact Integration with iPhone\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/google-calendar-contact-integration-with-iphone-a47dcfc5ce34", true);
      break;
    case "\nNewegg Computer Combo Assembly\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/newegg-computer-combo-assembly-aa276d3fcfc4", true);
      break;
    case "\nTI FRAM MSP-EXP430 Overview\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/ti-fram-msp-exp430-overview-cb0623bae6da", true);
      break;
    case "\nHomemade PID Controlled Hotplate\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/homemade-pid-controlled-hotplate-57a031358ca0", true);
      break;
    case "\nLinksys LED Matrix\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/linksys-led-matrix-470663a3d7ea", true);
      break;
    case "\nMultimeter Fuse Hack\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/multimeter-fuse-hack-21fb2449b602", true);
      break;
    case "\nLinksys LED Matrix (Intro)\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/linksys-led-matrix-intro-cd11b9fc2ac3", true);
      break;
    case "\nFlower Garden &amp; Border\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/flower-garden-border-d760ff94e0a", true);
      break;
    case "\nGarden Soaker Hose Tip\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/garden-soaker-hose-tip-b66c397364d6", true);
      break;
    case "\nMicro SD Card Keychain Dissasembly\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/micro-sd-card-keychain-dissasembly-36a069633d31", true);
      break;
    case "\nDVD Rack\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/dvd-rack-ea0f67b6ba0d", true);
      break;
    case "\nGardening\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/gardening-1ec000ebc3a8", true);
      break;
    case "\nIntroduction\n":
      checkCookie("https://medium.com/my-life-as-a-tinkerer/introduction-b62448839ebb", true);
      break;
    default:
      // not found - just redirect to homepage
      checkCookie("https://medium.com/my-life-as-a-tinkerer/", true);
      break;
  }
}
</script>