Why is javascript not making the value more than 1 using the +1

I can not make the output number bigger than one when I click a button I a using the +1 operator.
I have search everywhere but just can not find a easy and good solution.

echo <<<_END
    
<p>You have </p><a href="#" id="more" class="list-group-item disabled">0 </a>
<script>
function more(){
           document.getElementById("more").innerHTML = +1;//plus one
        }
</script>
_END;
    echo <<<_END
        <img src="coin.png" width="2%" alt="coins">
    _END;
    echo <<<_END
    <button onClick="more()">More!</button>//the button
    
    _END;
    
    ?>