javascript 파라미터 값 받기

function 구문

<script>
function getParameter(name) {
    name = name.replace(/[[]/, "[").replace(/[]]/, "]");
    var regex = new RegExp("[?&]" + name + "=([^&#]*)"),
        results = regex.exec(location.search);
    return results === null ? "" : decodeURIComponent(results[1].replace(/+/g, " "));
}
</script>

스크립트 
URL :  test.com?user_name=admin&id=relation 

<script>
var id = getParameter("id");
var user_name = getParameter("user_name");

console.log("id : "+id);
console.log("user_name : "+user_name);
</script>