How can we get JavaScript array by JSP scriptlet

Just let Java/JSP print a syntactically valid JS array syntax. Keep in mind that Java/JSP and JavaScript doesn't run in sync. Java/JSP produces HTML as one large String and JS is just part of it. JS ultimately runs in the webbrowser once it has retrieved all that HTML output from Java/JSP.

Assuming that you ultimately want the following valid JS array syntax:

<script type="text/javascript">
    var strComboValue = [ "one", "two", "three" ];
</script>

Then you should write your Java/JSP code accordingly so that it prints exactly that syntax:

<script type="text/javascript">
    var strComboValue = [ 
<% 
    String[] options = DBComboOptions.getOptions(combos);
    for (int i = 0; i < options.length; i++) {
%>
        "<%= options[i] %>"
<%
        if (i + 1 < options.length) {
%>
            ,
<%
        }
    }
%>
    ];
</script>

It's only terribly unreadable (and not only because of using old fashioned scriptlets instead of taglibs). Easier, however, is to grab a JSON (JavaScript Object Notation) library like Google Gson and create an additional method getOptionsAsJson() which does something like the following:

public getOptionsAsJson(Object value) {
    return new Gson().toJson(getOptions(value));
}

And finally use it instead:

<script type="text/javascript">
    var strComboValue = <%=DBComboOptions.getOptionsAsJson(combos)%>;
</script>