JS copy textarea button

Hi guys, i'm a grade 9 student and struggling with my small JS project. my teacher wants me to create a password generator. he wants me to create a Copy button that copies the random password that will display the word "copied" and display "field is empty" when blank. so far this is what i have

</style>

</head>
<script language="javascript" type="text/javascript">
function randomString() {
    var chars = "00112233445566778899AaBbCcDdEdFfGgHhIiJjKkLLMmNnOoPpQqRrSsTtUuVvWwXxYyZz";
    var string_length = 8;
    var randomstring = '';
    for (var i=0; i<string_length; i++) {
        var rnum = Math.floor(Math.random() * chars.length);
        randomstring += chars.substring(rnum,rnum+1);
    }
    document.randform.randomfield.value = randomstring;
}

// Start copy button here

function copy() {
  let textarea = document.getElementById("myInput");
  textarea.select();
  document.execCommand("copy");
}

// END copy button

</script>


<form name="randform" align="center">
<input type="button"
    style="font-family:Consolas;color:#FFFFFF"
    class="button button1"
    value="Generate"
    onClick="randomString();">&nbsp;
<input type="text"
    id="myInput"
    name="randomfield"
    value=""
    style="color:blue; padding: 12px 16px; font-size:20px; font-family:Consolas; font-weight:bold; background:#FCF4A3; width: 10%;">&nbsp

<input type="button"
    style="font-family:Consolas;color:#FFFFFF"
    class="button copybtn"
    value="COPY"
    onClick="copy('myInput');">&nbsp;


</form>

HTML:

 

Here's a snippet you could use:

function copyInput(id) {
//Get input field reference
var inputField = document.getElementById(id);

//Select the text
inputField.select();

//Execute the copy command
document.execCommand("copy");

//BOOM
alert(inputField.value + "copied to Clipboard");

Code (JavaScript):

Then call the method like:

onClick="copyInput('myInput');">

Code (JavaScript):

 

Thanks for looking into this
I tried it but it doesn't generate password anymore