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TS Null

The null type in TypeScript represents a variable that has been explicitly set to no value. It is useful for indicating the intentional absence of an object value.

Key Topics

Null Basics

In TypeScript, null is a value that represents the intentional absence of any object value.

let value: null = null;
console.log(value); // null

Output

null

Explanation: The variable value is explicitly assigned the null value, indicating the absence of a value.

Strict Null Checks

When strictNullChecks is enabled in TypeScript, null and undefined are not assignable to other types unless explicitly stated.

// strictNullChecks: true
let nullable: string | null = null;
nullable = "TypeScript";
console.log(nullable); // TypeScript

Output

TypeScript

Explanation: The nullable variable can hold a value of type string or null due to the explicit union type declaration.

Optional Properties

Optional properties in interfaces or types are implicitly undefined if not assigned, but they can be explicitly set to null if needed.

interface User {
    id: number;
    name?: string | null;
}

const user: User = { id: 1, name: null };
console.log(user); // { id: 1, name: null }

Output

{ id: 1, name: null }

Explanation: The name property in the User interface is optional and can explicitly hold a null value.

Nullish Coalescing

The ?? operator, known as the nullish coalescing operator, returns its right-hand operand when the left-hand operand is null or undefined.

const input = null;
const result = input ?? "Default Value";
console.log(result); // Default Value

Output

Default Value

Explanation: The result variable is assigned "Default Value" because input is null. The nullish coalescing operator ensures fallback values are used for null or undefined.

Key Takeaways

  • Null Basics: null represents the intentional absence of a value.
  • Strict Null Checks: Prevent assigning null or undefined to variables unless explicitly allowed.
  • Optional Properties: Use null for explicitly indicating no value in optional properties.
  • Nullish Coalescing: Use the ?? operator to handle null or undefined values gracefully.
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