array_map_syntax_sugar.ts

type MapProxyValue<T> = T extends (...args: infer U) => infer V
  ? (...args: U) => V[]
  : T[]
type MapProxy<T> = {
  [key in Exclude<keyof T, '_avoid_ts_something'>]: MapProxyValue<T[key]>
}

class Array2<T> extends Array<T> {
  map2<U>(f: (v: T) => U): U[]
  map2(): MapProxy<T>
  map2(f?: (v: T) => any) {
    if (f) return this.map(f)
    return new Proxy(this, {
      get(arr: T[], prop: string) {
        if (arr.every(v => typeof v[prop] === 'function')) {
          return (...args: any[]) => arr.map(v => v[prop](...args))
        } else {
          return arr.map(v => v[prop])
        }
      }
    }) as any
  }
}

console.log(new Array2('a', 'bc', 'def').map2(a => a.length))
console.log(new Array2('a', 'bc', 'def').map2().length)
console.log(new Array2('a', 'bc', 'def').map2().substr(1))
console.log(new Array2('a', 'bc', 'def').map2().substr(1,1))

sample.js

const originalMap = Array.prototype.map
Array.prototype.map = function(f) {
  if (f) return originalMap.call(this, f)
  return new Proxy(this, {
    get(arr, prop) {
      if (arr.every(v => typeof v[prop] === 'function')) {
        return (...args) => originalMap.call(arr, v => v[prop](...args))
      } else {
        return originalMap.call(arr, v => v[prop])
      }
    }
  })
}

;['a', 'bc', 'def'].map().length // => [1, 2, 3]
;['a', 'bc', 'def'].map().substr(1,2) // => ["", "c", "ef"]