first-item.ts

import type { PrototypeStruct } from '../index.js';

interface FirstItem<T> {
  firstItem(): T | undefined;
}

export const firstItem: PrototypeStruct = {
  label: 'firstItem',
  fn: function arrayFirstItem<T>(): T | undefined {
    const ctx = this as unknown as T[];
    const len = ctx.length;

    if (!len) return void 0;
    if (1 === len) return ctx[0];
    return ctx.slice(0, 1)[0];
  },
};

declare global {
  interface Array<T> extends FirstItem<T> {}
}