const f1: {(): number}
const f2: () => number
// This is an error because the syntax is not correct:
// let f3: {() => number} // error TS1005: ':' expected.
Are the declarations of f1 and f2 equivalent?
Why does f3 result in an error?
const f1: {(): number}
const f2: () => number
// This is an error because the syntax is not correct:
// let f3: {() => number} // error TS1005: ':' expected.
Are the declarations of f1 and f2 equivalent?
Why does f3 result in an error?
Utilizing braces in the notation allows for defining overload method signatures and/or hybrid types. Take, for instance:
interface Foo {
(x: number): void,
(x: string): void,
bar: string,
}
This example showcases two call signatures and one property labeled bar.
In cases where there is only one call signature and no properties present, a shorthand syntax - similar to the one used for f2 - can be employed. When using braces, arguments should be separated from the return type with a colon (:), whereas the shorthand syntax utilizes =>.
These two are not the same.
The structure of function f1 typically involves an object literal. However, if there is only one call signature with no properties, it is recommended to omit the { } braces to prevent any confusion.
If the return type needs to be a function, then f2 is the better choice.
When using an object literal, you can define keys and their corresponding return values. For example:
let f5: {name: string, ageFn: () => number};
Considering the above example, it becomes evident why f3 is considered invalid.
Absolutely, it is possible to define the return type of functions.
const myFunction = function (): string {}
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