Function to_object 

pub fn to_object(v: &Value) -> Value

ToObject(v) (7.1.18) for a primitive: the wrapper object with the matching prototype and a [[StringData]]/[[NumberData]]/[[BooleanData]] slot.

A String wrapper also owns its index properties and length, which is what makes w[0], w.length and Object.keys(w) answer; all of them are non-writable and non-configurable, as the exotic String object’s are.