Do you think this is a clever way to circumvent using ENUM for a parameter?

Question

Do you think this is a clever way to circumvent using ENUM for a parameter?

As I continue to explore different coding styles in Typescript and Angular, I recently encountered a method without any comments attached to it.

It seems like this method is enforcing that the value passed in must be one of the defined options, but strangely, it does not utilize ENUM for enforcement. This lack of documentation could potentially cause issues in a large codebase.

Is my understanding correct that this method requires the value to be equal to one of the || options?

static getEndpoint = (type: string = 'alpha' || 'bravo' || 'charlie) => {}

In my opinion, utilizing an ENUM would have been a better approach:

export enum MyTypes {
  ALPHA = 'alpha',
  BRAVO = 'bravo',
  CHARLIE = 'charlie',
}

And then modifying the method like this:

static getEndpoint = (type: MyTypes = MyTypes.ALPHA) => {}

angular typescript

Answer 1

Answer №1

In the hypothetical scenario:

static getEndpoint = (type: 'alpha' | 'bravo' | 'charlie' = 'alpha') => {}

then indeed. However, at present, it will permit any string input and default to 'alpha'. This is due to:

(type: string = 'alpha' || 'bravo' || 'charlie')
//     ^^^^^^   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
//       |                  \ the default value, 
//       |                    which results in: 'alpha'
//       |
//       \-- the actual type (in this case: string)

Reference: Literal Types

Answer 2

In the hypothetical scenario:

static getEndpoint = (type: 'alpha' | 'bravo' | 'charlie' = 'alpha') => {}

then indeed. However, at present, it will permit any string input and default to 'alpha'. This is due to:

(type: string = 'alpha' || 'bravo' || 'charlie')
//     ^^^^^^   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
//       |                  \ the default value, 
//       |                    which results in: 'alpha'
//       |
//       \-- the actual type (in this case: string)

Reference: Literal Types

Answer 3

Answer №2

The code displayed is unable to compile due to a missing '. However, assuming you have this:

static getEndpoint = (type: string = 'alpha' || 'bravo' || 'charlie') => {}

then no, the code does not enforce anything other than the requirement for type to be a string. Essentially, the code above is no different from:

static getEndpoint = (type: string = 'alpha') => {}

The section after the = sign represents a default parameter value, and the expression 'alpha' || 'bravo' || 'charlie' will always evaluate to 'alpha'.

It seems like it was supposed to be written as follows:

static getEndpoint = (type: 'alpha' | 'bravo' | 'charlie') => {}

This uses a union of string literal types, requiring the type passed for type to be either "alpha", "bravo", or "charlie". For example:

getEndpoint("alpha");

However, passing a variable like s even if it contains the string "alpha" without verification at compile-time would not work:

let s: string;
// ...something setting `s`...
getEndpoint(s);

In this form, using a union of string literal types serves a similar function to an enum.

If it were up to me, I would have approached it differently...

You've introduced two modifications there:

Employing an enum design
Offering a distinct default value — well, technically it's the same but done intentionally :-)

Your version works fine, but if you prefer string literal types, it would appear like this:

static getEndpoint = (type: 'alpha' | 'bravo' | 'charlie' = 'alpha') => {}

Answer 4

The code displayed is unable to compile due to a missing '. However, assuming you have this:

static getEndpoint = (type: string = 'alpha' || 'bravo' || 'charlie') => {}

then no, the code does not enforce anything other than the requirement for type to be a string. Essentially, the code above is no different from:

static getEndpoint = (type: string = 'alpha') => {}

The section after the = sign represents a default parameter value, and the expression 'alpha' || 'bravo' || 'charlie' will always evaluate to 'alpha'.

It seems like it was supposed to be written as follows:

static getEndpoint = (type: 'alpha' | 'bravo' | 'charlie') => {}

This uses a union of string literal types, requiring the type passed for type to be either "alpha", "bravo", or "charlie". For example:

getEndpoint("alpha");

However, passing a variable like s even if it contains the string "alpha" without verification at compile-time would not work:

let s: string;
// ...something setting `s`...
getEndpoint(s);

In this form, using a union of string literal types serves a similar function to an enum.

If it were up to me, I would have approached it differently...

You've introduced two modifications there:

Employing an enum design
Offering a distinct default value — well, technically it's the same but done intentionally :-)

Your version works fine, but if you prefer string literal types, it would appear like this:

static getEndpoint = (type: 'alpha' | 'bravo' | 'charlie' = 'alpha') => {}

Do you think this is a clever way to circumvent using ENUM for a parameter?

Answer №1

Answer №2

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