Improving the method to change a string into a string literal in TypeScript

Question

Improving the method to change a string into a string literal in TypeScript

Utilizing a third-party tool that has specified

editorStylingMode?: 'outlined' | 'underlined' | 'filled';

I have set the value in my environment.ts file (in Angular) as shown below

export const environment = {
    production: true,
    editorStylingMode: 'filled'
};

This leads to an error in my code while assigning the value from the environment

config({
    editorStylingMode: environment.editorStylingMode,
});

Type 'string' is not assignable to type '"filled" | "outlined" | "underlined"'

I tested the following solutions and they both resolve the issue

Solution 1

    config({
        editorStylingMode: environment.editorStylingMode as 'filled' | 'outlined' | 'underlined',
    });

Solution 2

export const environment: {
    production: boolean,
    editorStylingMode: 'filled' | 'outlined' | 'underlined',
} = {
    production: false,
    editorStylingMode: 'filled'
};

Is there a more efficient way to handle this situation?

angular typescript

Answer 1

Answer №1

If you want your environment to be read-only (assuming the intention is for it to be immutable even though using const doesn't guarantee deep immutability), you can utilize the as const assertion on the environment object:

export const environment = {
    production: true,
    editorStylingMode: 'filled'
} as const;

This approach not only makes the object type readonly, but it also preserves all literal types. Alternatively, you can apply as const directly on the field to retain the literal type:

export const environment = {
    production: true,
    editorStylingMode: 'filled' as const
};

However, both of these options may lead to issues if TypeScript determines that a specific branch cannot be taken due to the values being too specific. To avoid redundancy, another option is to use a type query to access the desired union:

export const environment = {
    production: true,
    editorStylingMode: 'filled' as Exclude<TypeFromLibThatContainsTheField['editorStylingMode'], null | undefined>
};

If referencing that type is not possible, you can utilize the function parameter instead:

export const environment = {
    production: true,
    editorStylingMode: 'filled' as Exclude<Parameters<typeof config>[0]['editorStylingMode'], null | undefined>
};

While these approaches may not necessarily be shorter, they help in avoiding repetition.

Answer 2

If you want your environment to be read-only (assuming the intention is for it to be immutable even though using const doesn't guarantee deep immutability), you can utilize the as const assertion on the environment object:

export const environment = {
    production: true,
    editorStylingMode: 'filled'
} as const;

This approach not only makes the object type readonly, but it also preserves all literal types. Alternatively, you can apply as const directly on the field to retain the literal type:

export const environment = {
    production: true,
    editorStylingMode: 'filled' as const
};

However, both of these options may lead to issues if TypeScript determines that a specific branch cannot be taken due to the values being too specific. To avoid redundancy, another option is to use a type query to access the desired union:

export const environment = {
    production: true,
    editorStylingMode: 'filled' as Exclude<TypeFromLibThatContainsTheField['editorStylingMode'], null | undefined>
};

If referencing that type is not possible, you can utilize the function parameter instead:

export const environment = {
    production: true,
    editorStylingMode: 'filled' as Exclude<Parameters<typeof config>[0]['editorStylingMode'], null | undefined>
};

While these approaches may not necessarily be shorter, they help in avoiding repetition.

Answer 3

Answer №2

A cleaner approach is illustrated below:

Interface.environments.ts:

  export interface InterfaceEnvironment {
      mode: 'light' | 'dark' | 'colorful';
}

Environments.ts:

import { InterfaceEnvironment } from './interface.environments';

export const environments: Environment = {
  mode: 'dark',
};

This method involves creating an interface which clearly defines the required properties for the environment object.

Answer 4

A cleaner approach is illustrated below:

Interface.environments.ts:

  export interface InterfaceEnvironment {
      mode: 'light' | 'dark' | 'colorful';
}

Environments.ts:

import { InterfaceEnvironment } from './interface.environments';

export const environments: Environment = {
  mode: 'dark',
};

This method involves creating an interface which clearly defines the required properties for the environment object.

Answer 5

Answer №3

To streamline your type assertions and maintain consistency throughout your application, consider defining a new type called EditorStylingMode. This way, you can easily expand the valid values for EditorStylingMode without having to update multiple instances of the values in your code.

One approach is to export the environment like this:

export const environment = {
    production: true,
    editorStylingMode: 'filled' as EditorStylingMode,
};

Your config setup would then simply be:

config({
    editorStylingMode: environment.editorStylingMode,
})

Alternatively, you could define an interface for environment and export it separately:

// environment.js
export interface Environment {
    production: boolean;
    editorStylingMode: EditorStylingMode,
}

export const environment: Environment = {
    production: true,
    editorStylingMode: 'filled',
};

By using one of these solutions, you not only ensure that environment remains correctly typed but also have the option to import and utilize the Environment type in other parts of your code. This enables you to declare config with strong typing as demonstrated below:

// config.js
import { Environment } from "./environment";

export function config(env: Environment) { ... }

...

// main.js
import { environment } from "./environment";
import { config } from "./config";

config(environment);

Answer 6

To streamline your type assertions and maintain consistency throughout your application, consider defining a new type called EditorStylingMode. This way, you can easily expand the valid values for EditorStylingMode without having to update multiple instances of the values in your code.

One approach is to export the environment like this:

export const environment = {
    production: true,
    editorStylingMode: 'filled' as EditorStylingMode,
};

Your config setup would then simply be:

config({
    editorStylingMode: environment.editorStylingMode,
})

Alternatively, you could define an interface for environment and export it separately:

// environment.js
export interface Environment {
    production: boolean;
    editorStylingMode: EditorStylingMode,
}

export const environment: Environment = {
    production: true,
    editorStylingMode: 'filled',
};

By using one of these solutions, you not only ensure that environment remains correctly typed but also have the option to import and utilize the Environment type in other parts of your code. This enables you to declare config with strong typing as demonstrated below:

// config.js
import { Environment } from "./environment";

export function config(env: Environment) { ... }

...

// main.js
import { environment } from "./environment";
import { config } from "./config";

config(environment);

Improving the method to change a string into a string literal in TypeScript

Solution 1

Solution 2

Answer №1

Answer №2

Answer №3

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