Array.isArray( ) with readonly []

[jonlepage]

🔎 Search Terms

Array.isArray( )

🕗 Version & Regression Information

• This changed between versions ______ and _______
• This changed in commit or PR _______
• This is the behavior in every version I tried, and I reviewed the FAQ for entries about _________
• I was unable to test this on prior versions because _______

⏯ Playground Link

Playground

💻 Code

// from: ms-vscode.vscode-typescript-next-5.9.20250307\node_modules\typescript\lib\lib.es5.d.ts
interface ArrayConstructor {
    new (arrayLength?: number): any[];
    new <T>(arrayLength: number): T[];
    new <T>(...items: T[]): T[];
    (arrayLength?: number): any[];
    <T>(arrayLength: number): T[];
    <T>(...items: T[]): T[];
    isArray(arg: any): arg is readonly any[]; // <== fix the Array.isArray() ✅
    isArray(arg: any): arg is any[];
    readonly prototype: any[];
}

//ex: this will work fine now 
	public hasStatus( entityWithStates: EntityWith<C.StatesComponent>, status: STATUS | readonly STATUS[]  ) {
		const { statesMap } = entityWithStates.get( C.StatesComponent ).read;
		return Array.isArray( status ) ? status.some( ( _status ) => statesMap.has( _status ) ) : statesMap.has( status );
	}

🙁 Actual behavior

type became any[]

🙂 Expected behavior

support readonly array when do a Array.isArray()

Additional information about the issue

No response

[jcalz]

duplicate #17002, also see #55238, #53395, #57566, etc

[jonlepage]

duplicate #17002, also see #55238, #53395, #57566, etc

Thank you friend.
Do you know if, by adding this line in my project, I might encounter problems?
isArray(arg: any): arg is readonly any[];
I have tested it on 3 or 4 scenarios without any issues and it fix my issue, but I assume that if this issue has been running for more than ~8years, it might because it will break the entire ts somewhere?
Playground

However, when I add this line to the Array constructor, the issue is resolved, but I have a slight doubt. Indeed, if a team hasn't added this change, it maybe because it can inevitably lead to more serious issues?
I've learned to be cautious when everything seems too simple to be true.

[typescript-bot]

This issue has been marked as "Duplicate" and has seen no recent activity. It has been automatically closed for house-keeping purposes.