I don't know why the error is happening: Uncaught SyntaxError: Unexpected token ':'

Uncaught SyntaxError: Unexpected token ':'

<script>
    function createLink(){
        const div3 = document.getElementById("div3");
        if(!div3.hasChildNodes()){
            consta1 = document.createElement("a");
            a1.href='+{route('alink')}}+';
            a1.innerText="itsakura";
            div3.appendChild(a1);
        }
    }