Use

A can-view-scope represents a lookup context and parent contexts that can be used to look up a key value.

If no parent scope is provided, only the scope’s context will be explored for values. For example:

var data = {name: {first: "Justin"}};
var scope = new Scope(data);

scope.get("name.first") //-> "Justin"
scope.get("length")     //-> undefined

However, if a parent scope is provided, key values will be searched in the parent’s context after the initial context is explored. For example:

var list = [{name: "Justin"}, {name: "Brian"}];
var justin = list[0];

var listScope = new Scope(list);
var curScope = new Scope(justin, listScope);

curScope.get("name") //-> "Justin"
curScope.get("length") //-> 2

Use add to easily create a new scope from a parent scope like:

var list = [{name: "Justin"}, {name: "Brian"}];
var justin = list[0];

var curScope = new Scope(list).add(justin);

curScope.get("name") //-> "Justin"
curScope.get("length") //-> 2