print-type

Prints fully-expanded Typescript types from variables, type aliases, etc. to a string (API) or the terminal (CLI).

Reference docs: https://electrovir.github.io/print-type/

Install

npm i -D print-type
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Or, if you want to use this everywhere:

npm i -g print-type
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Usage

(npx should be omitted if you installed this package globally.)

npx print-type <path-to-file.ts> <name-to-expand> [--deep]
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• <name-to-expand>: the name of the thing to expand, whether it be a variable, a type definition, anything.
• <path-to-file.ts>: path to the file that contains the name of the thing to expand.
• -deep: optional flag that recurses even deeper into types.

Examples

Big type compared to VS Code

This is an example taken from this package's own test files. You can see the example file here: all-the-types.ts.

npx print-type test-files/all-the-types.ts ComplexType
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VS Code output

This is all that a VS Code hover will give you. Note the "... 11 more ...;" truncation. Even setting "noErrorTruncation": true in your tsconfig isn't always enough to remedy this.

{
    id: string;
    name: string;
    age?: number;
    readonly createdAt: Date;
    status: "active" | "inactive" | "pending" | "archived";
    priority: 1 | 2 | 3 | 4 | 5;
    address: {
        street: string;
        city: string;
        zipCode: string;
        country: string;
        coordinates?: {
            lat: number;
            lng: number;
        };
    };
    ... 11 more ...;
    workflow: {
        steps: Array<{
            id: string;
            type: "validation" | "transformation" | "output";
            config: Record<string, any>;
            dependencies?: string[];
            parallel?: boolean;
        }>;
        triggers: {
            manual: boolean;
            scheduled?: {
                cron: string;
                timezone: string;
            };
            webhook?: {
                url: string;
                secret: string;
            };
        };
    };
}
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print-type output

This package prints the following (the full type, even with comments!):

{
    // Basic properties
    id: string;
    name: string;
    age?: number;
    readonly createdAt: Date;

    // Union types
    status: 'active' | 'inactive' | 'pending' | 'archived';
    priority: 1 | 2 | 3 | 4 | 5;

    // Nested objects
    address: {
        street: string;
        city: string;
        zipCode: string;
        country: string;
        coordinates?: {
            lat: number;
            lng: number;
        };
    };

    // Arrays and complex collections
    tags: string[];
    scores: number[];
    metadata: Record<string, unknown>;
    permissions: Array<{
        resource: string;
        actions: ('read' | 'write' | 'delete')[];
        granted: boolean;
    }>;

    // Function types
    validate: (input: string) => boolean;
    transform: <T>(data: T) => T;
    onUpdate?: (changes: Partial<ComplexType>) => void;

    // Generic and mapped types
    cache: Map<string, any>;
    settings: {
        [K in 'theme' | 'language' | 'timezone']: string;
    } & {
        notifications: {
            email: boolean;
            push: boolean;
            sms?: boolean;
        };
    };

    // Conditional and template literal types
    apiEndpoints: {
        [K in `get${Capitalize<string>}` | `post${Capitalize<string>}`]: string;
    };

    // Intersection and utility types
    profile: Pick<ComplexType, 'name' | 'age'> & {
        bio?: string;
        avatar?: string;
    };

    // Complex nested structure
    workflow: {
        steps: Array<{
            id: string;
            type: 'validation' | 'transformation' | 'output';
            config: Record<string, any>;
            dependencies?: string[];
            parallel?: boolean;
        }>;
        triggers: {
            manual: boolean;
            scheduled?: {
                cron: string;
                timezone: string;
            };
            webhook?: {
                url: string;
                secret: string;
            };
        };
    };
}
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