You can use named parameters in your function like this:
var insertUser = edge.func('sql', function () {/*
INSERT INTO dbo.Newsletter (Email, Active, DateCreated, DateUpdated, Deleted)
VALUES (@emailAddress,'1','2014-01-01 00:00:00','2014-01-01 00:00:00','0')
*/});
Pass it an object with parameters like this:
var emailAddress = document.getElementById('emailInput').value;
insertUser({"emailAddress": emailAddress}, callBack)