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Limit Use of the any Type

There’s No Type Safety with any Types

let ageInYears: number;
ageInYears = '12';
// ~~~~~~~ Type 'string' is not assignable to type 'number'.
ageInYears = '12' as any; // OK
ageInYears += 1; // OK; at runtime, ageInYears is now "121"

any Lets You Break Contracts

function calculateAge(birthDate: Date): number {
 // ...
}
let birthDate: any = '1990-01-19';
calculateAge(birthDate); // OK

There Are No Language Services for any Types

any Types Mask Bugs When You Refactor Code

any Hides Your Type Design

any Undermines Con‚dence in the Type System

Things to Remember

• TypeScript’s any type allows you to disable most forms of type checking for a symbol.
• The any type eliminates type safety, lets you break contracts, harms developer experience, makes refactoring error prone, hides your type design, and undermines confidence in the type system.
• Avoid using any when you can!