Repository navigation
generate function declaration from function type in TypeScript #22395
Description
From Homa Wong (@unional) on October 5, 2017 18:52
type MyCallback = (a: number, b: string) => void
function foo(callback: MyCallback) {
// ...
}
// case 1
foo((a, b) => { ... })
// case 2
foo(function (a, b) { ... })
// case 3
function cb(a: number, b: string) { ... }
foo(cb)Above are 3 common ways to write a callback.
TypeScript is great at inferring the argument types in the implemented callbacks.
a, and b are typed accordingly in the callbacks above.
However, the tooltip is not useful when we are implementing the callbacks:
If I change foo() to not using type alias, it helps in case 1 and 2:
function foo(callback: (a: number, b: string) => void) { ... }
But that doesn't help in case 3 and actually demotes type alias.
One solution I can think of is using [ctrl+.] to fill in the callback:
foo(/* caret */)
// [ctrl+.] and choose "implement callback as arrow function":
foo((a: number, b: string) => { /* caret */ })
// [ctrl+.] and choose "implement callback as function declaration":
foo(function (a: number, b: string) { /* caret */ })
// caret anywhere on the type alias below
MyCallback
// [ctrl+.] and choose "implement function declaration" will expand to snippet:
function ${1:functionName}(a: number, b: string): void { ${0} }Copied from original issue: microsoft/vscode#35635
Activity
ackvf commentedon Apr 10, 2022
This is really great! It's sometimes hard to follow the hints, having TS write a new arrow function in there for me with all the parameters leaving me only to write the function body is just great 🤩