How to select from list and click submit button then go to link "in HTML"

I found this code for my project. I want to change this to open website with click on submit button

<html>
<body>
<form action="/action_page.php" method="get">
  <label for="cars">Choose a Site:</label>
  <select id="site" name="site">
    <option value="Google">Google</option>
    <option value="Yahoo">Yahoo</option>
    <option value="MSN">MSN</option>
  </select>
  <input type="submit">
</form>
</body>
</html>

for example: when select "Google" from list, with click on "submit" button open "www.google.com" that exist on "action_page.php"

I dont have "action_page.php" code

Solution

Firstly, I modified your html code:

<html>
<body>
<form method="get">
  <label for="cars">Choose a Site:</label>
  <select id="site" name="site">
    <option value="Google">Google</option>
    <option value="Yahoo">Yahoo</option>
    <option value="MSN">MSN</option>
  </select>
</form>
<button type="button" id="button" >Submit</button>

<script src="script1.js"></script>
</body>
</html>

Made a button outside of the form and referenced the external js file script1.js

Then I created the js file and added this code to it:

var select = document.getElementById('site');

document.getElementById("button").onclick = function(){
    var value = select.value
    if (value == "Google")
    {
        window.location.href = "https://www.google.com/";
    }
    else if (value == "Yahoo")
    {
        window.location.href = "https://www.yahoo.com/";
    }
    else if (value == "MSN")
    {
        window.location.href = "https://www.msn.com/";
    }
};

It finds the select tag and the button from the html script, checks if the button was pressed and redirects to the corresponding website based on the dropdown selection.