caml query for filtering list item not working as expected in Sharepoint hosted app

I am trying to filter list item based on particular value.

var header = "xyz";
camlQueryHeader.set_viewXml = "<view><Query><Where><Eq><FieldRef Name='Position'/>" + "<Value Type='Text'>" + header + "</Value></Eq></Where></Query></view>";

Instead of getting filtered list items, I get all the list items. What am I missing?

Note: I am creating Sharepoint hosted app using CSOM.

regards, Ritesh Anand