When facing difficulties, I have an array with functions, such as:
this._array = [handler, func, type]
How should I declare this private property?
1. Array<any>
2. any[]
3. T[]
4. Array<T>
What is the difference in these declarations?
Here is another question:
this._array.push(()=>{ console.log("hey")})
How can I define the type of function in this case?
If you are unsure about the types that can be in your array, using any[] is not recommended. It would be better to refactor your code so that arrays have consistent types.
1) Array<any> - accepts any type of element.
2) any[] - same as the previous one.
console.log([].constructor);
console.log((new Array()).constructor);3) T[] only contains elements of type T. This can be used with Generic
4) Array<T> is similar to the above.
Assuming 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[], and for strings, it will be string[]. The type replacing T comes from the <T> in the object creation statement.
When working with TypeScript, similar to JavaScript, you have the ability to manipulate arrays of values. There are two different ways to define array types in TypeScript. The first method involves stating the type of elements followed by [] to indicate an array of that specific element type:
let list: number[] = [1, 2, 3];
The second approach utilizes a generic array type, Array<elemType>:
let list: Array<number> = [1, 2, 3];
For additional information, please refer to this link: https://www.typescriptlang.org/docs/handbook/basic-types.html
Array<any> and any[] represent arrays with no type checking on items, it is best to avoid using these.T[] and Array<T> are arrays of a specific type T, providing compile-time type checking.If you want to store something like [handler, func, type]:
let array: Array<(param:number) => void> = []
This version ensures that the items added to the array match your handler signature.
Instead of using an array, you can opt for a tuple, like so:
private _array: [any, () => void, string];
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