I had Public declared Dictonary in code behind as :
Public dics As New Dictionary(Of String, String()) From { _
{"picture", New String() {".jpeg", ".jpg", ".png", ".bmp", ".gif", ".tif"}}, _
{"document", New String() {".doc", ".docx", ".txt", ".htm", ".html", ".xml", ".xaml", ".css"}}, _
{"excel", New String() {".xls", ".xlsx", ".xlt", ".xla"}}, _
{"pdf", New String() {".pdf"}}, _
{"zip", New String() {".7z", ".APK", ".BAT", ".rar", ".dll", ".jar", ".zip"}}, _
{"ppt", New String() {".ppt", ".pos", ".pps"}}}
Edit :
if i do like this
function myFunction() {
var dic = "<%= dics %>";
var array_keys = new Array();
var array_values = new Array();
for (var key in dic) {
alert(key);
}
}
will show alerts as 
How can i access this Dictonary in javascript to do some operations