TypeScript tips & tricks from: http://ideasintosoftware.com/typescript-advanced-tricks/

Omit.ts

// `Omit` omit specific keys from existing interface
type Diff<T extends string, U extends string> = ({[P in T]: P } & {[P in U]: never } & { [x: string]: never })[T];  
type Omit<T, K extends keyof T> = {[P in Diff<keyof T, K>]: T[P]};  

// `Omit` usage
type TCleanedUser = Omit<IUser, 'privateField1' | 'privateField2'>;

Projection.ts

// `Projection` for typecheck your projection specifiers,
// i.e., which fields should - or should not - be returned in the result.
type Projection<T> = Partial<Record<keyof T, 0 | 1>>;  

// `Projection` usage
MyCollection.find({}, {importantField: 1: anotherImportantField: 1} as Projection<IMyDoc>);