JSdoc how to tell that a function returns the same type as a parameter

Question

in C# you would write

T RandomFrom< T >( List< T > list ) {
    return list[ ( int ) Math.Floor( new Random().Next() * list.Count ) ];
}

How should I do the same when documenting a JS function? I tried:

/**
 * @type {*} T
 * @param {T[]} list
 * @returns {T} 
 */
function randomFrom ( list ) {
    return list[ Math.floor( Math.random() * list.length ) ];
}

But VS Code tells me randomFrom(list: any[]): any and I'd like it to be something like randomFrom(list: []): . How do I achieve that? Putting the T inside <> makes it an arrow function.

user_533976 · Answer

This works:

/**
 * @template T
 * @param {T} a
 * @returns {T}
 */
function (a){
  return a
}

Check out more: https://www.typescriptlang.org/docs/handbook/jsdoc-supported-types.html#template

JSdoc how to tell that a function returns the same type as a parameter

1 Answers