JS Dropdown in final project

Question

My final project is a conversion website. I am trying to make a dropdown menu that when you click one of the options in the DD, you are taken to another page. When I put in the following code (from W3 schools) and I click the dropdown box, my page keeps reloading. Why does it keep reloading rather than just showing whatever is in the dropdown list? I assume it is because it is within the < form >.

index.html

{% extends "layout.html" %}

{% block title %}
index
{% endblock %}

{% block main %}
<form action="{{ url_for('index') }}" method="post">
      <div class="dropdown">
      <button onclick="myFunction()" class="dropbtn">Choose a unit</button>
                <div id="myDropdown" class="dropdown-content">
                    <a href="#Length">Length</a>
                    <a href="#Time">Time</a>
                    <a href="#Mass">Mass</a>
                    <a href="#Temperature">Temperature</a>
                    <a href="#Volume">Volume</a>
                </select>
            </div>
            <div class="hero-convert">
                <label for="Convert">Convert:</label>
                <input autocomplete="off" autofocus class="form-control" name="amount" placeholder="how much?" type="text"/>
                <select class="form-control" id="sel1">
                    <option>pounds</option>
                    <option>kilograms</option>
                    <option>milligrams</option>
                    <option>ounces</option>
                    <option>ton</option>
                    <option>stones</option>
                    <option>micrograms</option>
                </select>
                to
                <select class="form-control" id="sel2">
                    <option>pounds</option>
                    <option>kilograms</option>
                    <option>milligrams</option>
                    <option>ounces</option>
                    <option>ton</option>
                    <option>stones</option>
                    <option>micrograms</option>
                </select>
            </div>
            <div class="hero-button">
                <button class="btn btn-default" type="submit">Convert</button>
            </div>
</form>
{% endblock %}

button.js

function myFunction() {
document.getElementById("myDropdown").classList.toggle("show");
}

// Close the dropdown menu if the user clicks outside of it
window.onclick = function(event) {
if (!event.target.matches('.dropbtn')) {

var dropdowns = document.getElementsByClassName("dropdown-content");
var i;
for (i = 0; i < dropdowns.length; i++) {
  var openDropdown = dropdowns[i];
  if (openDropdown.classList.contains('show')) {
    openDropdown.classList.remove('show');
  }
}
}
}

CSS

.dropbtn {
background-color: #4CAF50;
color: white;
padding: 16px;
font-size: 16px;
border: none;
cursor: pointer;
}

.dropbtn:hover, .dropbtn:focus {
background-color: #3e8e41;
}

.dropdown {
position: relative;
display: inline-block;
}

.dropdown-content {
display: none;
position: absolute;
background-color: #f9f9f9;
min-width: 160px;
overflow: auto;
box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
z-index: 1;
}

.dropdown-content a {
color: black;
padding: 12px 16px;
text-decoration: none;
display: block;
}

.dropdown a:hover {background-color: #f1f1f1}

.show {display:block;}

Answer 1

I took this all out of the form and it works. We will see what impact this has later in the mix.