Postgresql function to calculate current age
PostgreSQL includes many useful utility functions. One of those is the age function.
SELECT age(timestamp '1999-06-20'); age
-------------------------
20 years 3 mons 13 daysPosts tagged "function"
Typescript function parameter type
A previous post mentioned the Typescript ReturnType utility type. It is really handy to retrieve the return type of a function.
But there is also a type to retrieve the parameter list of a function. Meet Parameters<T>.
const add = (first: number, second: number) => first + second;
const cache = <T extends (...args: any) => any>(func: T) => {
const cacheObject = {};
return (...args: Parameters<T>) => {
const hashedArgs = JSON.stringify(args);
if (cacheObject.hasOwnProperty(hashedArgs)) {
return cacheObject[hashedArgs];
} else {
return (cacheObject[hashedArgs] = func(...args));
}
};
};See the full example here.
The code can be found at lib/lib.es5.d.ts:
/**
* Obtain the parameters of a function type in a tuple
*/
type Parameters<T extends (...args: any) => any> = T extends (...args: infer P) => any ? P : never;