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Generic Functions

Intermediate~18 min

Generic functions use type parameters to create flexible, reusable functions that work with multiple types.

Generic Functions

Output 
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Type Inference: TypeScript can automatically infer generic types from arguments, so you don't always need to specify them explicitly.

Multiple Type Parameters

function merge(obj1: T, obj2: U): T & U {
    return { ...obj1, ...obj2 };
}

let result = merge({ name: "Alice" }, { age: 25 });
// Type: { name: string } & { age: number }

Common Mistakes

1. Over-Specifying Types

// โœ— Redundant - TypeScript can infer
let result = map([1, 2], n => n.toString());

// โœ“ Better - let TypeScript infer
let result = map([1, 2], n => n.toString());

2. Not Using Return Type

// โœ— Loses type information
function wrap(value: T) {
    return { data: value };  // Type: { data: T }
}

// โœ“ Explicit return type
function wrap(value: T): { data: T } {
    return { data: value };
}
Best Practice: Let TypeScript infer types when possible. Only specify types explicitly when needed for clarity.

Summary

  • Generic functions use type parameters
  • TypeScript infers types from arguments
  • Multiple type parameters with <T, U>
  • Perfect for array operations and transformations
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