zig Tryit Editor

<!DOCTYPE html>
<html>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link href="https://fonts.googleapis.com/css?family=Raleway" rel="stylesheet">
<style>
* {
  box-sizing: border-box;
}
body {
  background-color: #f1f1f1;
}
#regForm {
  background-color: #ffffff;
  margin: 100px auto;
  font-family: Raleway;
  padding: 40px;
  width: 70%;
  min-width: 300px;
}
h1 {
  text-align: center;  
}
input {
  padding: 10px;
  width: 100%;
  font-size: 17px;
  font-family: Raleway;
  border: 1px solid #aaaaaa;
}
/* Mark input boxes that gets an error on validation: */
input.invalid {
  background-color: #ffdddd;
}
/* Hide all steps by default: */
.tab {
  display: none;
}
button {
  background-color: #04AA6D;
  color: #ffffff;
  border: none;
  padding: 10px 20px;
  font-size: 17px;
  font-family: Raleway;
  cursor: pointer;
}
button:hover {
  opacity: 0.8;
}
#prevBtn {
  background-color: #bbbbbb;
}
/* Make circles that indicate the steps of the form: */
.step {
  height: 15px;
  width: 15px;
  margin: 0 2px;
  background-color: #bbbbbb;
  border: none;  
  border-radius: 50%;
  display: inline-block;
  opacity: 0.5;
}
.step.active {
  opacity: 1;
}
/* Mark the steps that are finished and valid: */
.step.finish {
  background-color: #04AA6D;
}
</style>
<body>
<form id="regForm" action="https://www.w3schools.com/action_page.php">
  <h1>Register:</h1>
  
  <div class="tab">Name:
    <p><input placeholder="First name..." oninput="this.className = ''" name="fname"></p>
    <p><input placeholder="Last name..." oninput="this.className = ''" name="lname"></p>
  </div>
  <div class="tab">Contact Info:
    <p><input placeholder="E-mail..." oninput="this.className = ''" name="email"></p>
    <p><input placeholder="Phone..." oninput="this.className = ''" name="phone"></p>
  </div>
  <div class="tab">Birthday:
    <p><input placeholder="dd" oninput="this.className = ''" name="dd"></p>
    <p><input placeholder="mm" oninput="this.className = ''" name="nn"></p>
    <p><input placeholder="yyyy" oninput="this.className = ''" name="yyyy"></p>
  </div>
  <div class="tab">Login Info:
    <p><input placeholder="Username..." oninput="this.className = ''" name="uname"></p>
    <p><input placeholder="Password..." oninput="this.className = ''" name="pword" type="password"></p>
  </div>
  <div style="overflow:auto;">
    <div style="float:right;">
      <button type="button" id="prevBtn" onclick="nextPrev(-1)">Previous</button>
      <button type="button" id="nextBtn" onclick="nextPrev(1)">Next</button>
    </div>
  </div>
  
  <div style="text-align:center;margin-top:40px;">
    <span class="step"></span>
    <span class="step"></span>
    <span class="step"></span>
    <span class="step"></span>
  </div>
</form>
<script>
  var currentTab = 0; // Current tab is set to be the first tab (0)
  showTab(currentTab); // Display the current tab
  function showTab(n) {
    // This function will display the specified tab of the form...
    var x = document.getElementsByClassName("tab");
    x[n].style.display = "block";
    //... and fix the Previous/Next buttons:
    if (n == 0) {
      document.getElementById("prevBtn").style.display = "none";
    } else {
      document.getElementById("prevBtn").style.display = "inline";
    }
    if (n == (x.length - 1)) {
      document.getElementById("nextBtn").innerHTML = "Submit";
    } else {
      document.getElementById("nextBtn").innerHTML = "Next";
    }
    //... and run a function that will display the correct step indicator:
    fixStepIndicator(n)
  }
  function nextPrev(n) {
    // This function will figure out which tab to display
    var x = document.getElementsByClassName("tab");
    // Exit the function if any field in the current tab is invalid:
    if (n == 1 && !validateForm()) return false;
    // Hide the current tab:
    x[currentTab].style.display = "none";
    // Increase or decrease the current tab by 1:
    currentTab = currentTab + n;
    // if you have reached the end of the form...
    if (currentTab >= x.length) {
      // ... the form gets submitted:
      document.getElementById("regForm").submit();
      return false;
    }
    // Otherwise, display the correct tab:
    showTab(currentTab);
  }
  function validateForm() {
    // This function deals with validation of the form fields
    var x, y, i, valid = true;
    x = document.getElementsByClassName("tab");
    y = x[currentTab].getElementsByTagName("input");
    // A loop that checks every input field in the current tab:
    for (i = 0; i < y.length; i++) {
      // If a field is empty...
      if (y[i].value == "") {
        // add an "invalid" class to the field:
        y[i].className += " invalid";
        // and set the current valid status to false
        valid = false;
      }
    }
    // If the valid status is true, mark the step as finished and valid:
    if (valid) {
      document.getElementsByClassName("step")[currentTab].className += " finish";
    }
    return valid; // return the valid status
  }
  function fixStepIndicator(n) {
    // This function removes the "active" class of all steps...
    var i, x = document.getElementsByClassName("step");
    for (i = 0; i < x.length; i++) {
      x[i].className = x[i].className.replace(" active", "");
    }
    //... and adds the "active" class on the current step:
    x[n].className += " active";
  }
</script>
</body>

</html>