Function prototypeOfClass

prototypeOfClass<T, Args extends any[] = any[]>(cls: ConstructorOf<T, Args>): T

get the prototype object of a class.

this is useful when you want to access bound-methods of an instance of a class, such as the ones declared as:

class X {
	methodOfProto() { }
}

these bound methods are not available via destructure of an instance, because they then lose their this context. the only functions that can be destructured without losing their this context are the ones declared via assignment:

class X {
	fn = () => { }
	fn2 = function () { }
}

Type Parameters

T
Args extends any[] = any[]

Parameters

cls: ConstructorOf<T, Args>

Returns T

Example

import { assertEquals } from "jsr:@std/assert"

const
	array_proto = prototypeOfClass(Array<number>),
	arr = [1, 2, 3, 4, 5]

array_proto.push.call(arr, 6)
assertEquals(arr, [1, 2, 3, 4, 5, 6])

const slow_push_to_arr = (...values: number[]) => (arr.push(...values))
// the following declaration is more performant than `slow_push_to_arr`,
// and it also has lower memory footprint.
const fast_push_to_arr = array_proto.push.bind(arr)

slow_push_to_arr(7, 8)  // sloww & bigg
fast_push_to_arr(9, 10) // quicc & smol
assertEquals(arr, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10])