CODEWITHSUNDEEP
javascripttypescript
Юра Панарин
Юра Панарин

Reputation: 849

What is best practice for TypeScript?

If have some troble, i have array with function, like:

this._array = [handler, func, type]

How i need declare this private Property:

 1. Array<any>
 2. any[]
 3. T[]
 4. Array<T>

What difference in this declaration?

And some question:

this._array.push(()=>{ console.log("hey")})

How i can define type function?

Upvotes: 1

Views: 2113

Answers (4)

Markus
Markus

Reputation: 4149

You can use a tuple instead of an array, eg.:

private _array: [any, () => void, string];

Upvotes: 0

Suren Srapyan
Suren Srapyan

Reputation: 68635

In you case if you don't know which types can be in your array use any[], which is not desired. I suggest you to refactor your code to have arrays with the same types.

1) Array<any> - accept anything.

2) any[] - is the same as above one.

console.log([].constructor);
console.log((new Array()).constructor);

3) T[] contains only elements which type is T. Can be used in Generic

4) Array<T> same as the above.

Saying you have a class 

class SomeClass<T> {
   items: Array<T>;
}

const numbers = new SomeClass<number>();
const strings = new SomeClass<string>();

For numbers the items will be of type number[], for strings it will be string[]. The type which will replace T is got from the <T> in the object creation statement.

Upvotes: 2

Titian Cernicova-Dragomir
Titian Cernicova-Dragomir

Reputation: 249466

  1. Array<any> and any[] are equivalent and are arrays of anything (not type checking on items, best avoid these if you can help it)
  2. T[] and Array<T> are equivalent and are arrays of the given type T, so you will get compile type checking for these.

If you need to store something like [handler, func, type] :

   let arrary: Array<(param:number) => void> = []

With this version the items pushed are checked to conform to your handler signature.

Upvotes: 0

S M
S M

Reputation: 3233

TypeScript, like JavaScript, allows you to work with arrays of values. Array types can be written in one of two ways. In the first, you use the type of the elements followed by [] to denote an array of that element type:

let list: number[] = [1, 2, 3];

The second way uses a generic array type, Array<elemType>:

let list: Array<number> = [1, 2, 3];

More refer here : https://www.typescriptlang.org/docs/handbook/basic-types.html

Upvotes: 0

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