export const a= {
b:
(): c => (d, e) => {
return d+e
}
I am having trouble understanding what the code above does. I am confused by the usage of (): what exactly is the b function if it is translated into plain javascript? If I call a.b(), what actually happens?
The best way to find solutions to stuff like this is using the typescript online compiler. If you look here: http://www.typescriptlang.org/play/#code/C4TwDgpgBAxlC8UCGA7EBuAUJiAPMA9gE7CwEoDOpSCUA3plFAEYBcjTUAFAJSuwIAfNwAmAGigQeQ+h05QiEYAFciKKCKgBqSXKgBfTPqA
You can see that the function b returns the function:
(d, e) => {
return d+e
}
and this function is of type c.
(d: any, e:any)=>anywhat exactly is the b function if it is translated into plain javascript?
export const aJS = {
b: () => (d, e) => d + e
}
aJS.b()(3,4) // 7
So aJS.b is some kind of thunk or deferred function call.
In the TS version, c is a type. You can (1) leave out c and let the compiler infer the function type or (2) create a contextual function type and have the function arguments be inferred (code sample):
(1)
const a = {
b: () => (d: number, e: number) => d + e
}
a.b()(3, 4) // 7
(2)
type c = (n1: number, n2: number) => number
const a2 = {
b: (): c => (d, e) => d + e
}
a2.b()(3, 4) // 7
