As an answer I say No. You can only get values from jstl to javascript. But u can display the user name using javascript itself. Best ways are here. To display user name, if u have html like
<div id="uName"></div>
You can display user name as follows.
var val1 = document.getElementById('userName').value;
document.getElementById('uName').innerHTML = val1;
var userName = '<c:out value="${user}"/>';
here ${user} is the data you get as response(from backend).
var arrayLength = <c:out value="${details.size()}"/>;
function advanced(){
var values = new Array();
<c:if test="${empty details.users}">
values.push("No user found");
</c:if>
<c:if test="${!empty details.users}">
<c:forEach var="user" items="${details.users}" varStatus="stat">
values.push("${user.name}");
</c:forEach>
</:c:if>
alert("values[0] "+values[0]);
});