跳至主要内容

fill

🔸 題目描述

實作 fill 函式，此函式接收四個參數：

  • 一個陣列
  • 要替換的 value
  • start 索引
  • end 索引

該函式會從 start 到 end 索引 (包含 start 但不包含 end) 來把陣列的元素換成 value 。如果未提供 start 索引，則應預設為 0。如果未提供 end 索引，則剩餘元素會被替換為 value。

fill([1, 2, 3], "_");
// => ['_', '_', '_']

fill([1, 2], "*", 2, 3);
// => [1, 2]

fill([1, 2, 3, 4, 5], "_", 1, -1);
// => [1, '_', '_', '_', 5]

Tests​

import { describe, expect, test } from "@jest/globals";
import fill from "./fill"; // adjust this to your actual file path

describe("fill", () => {
  test("fills all elements with the provided value when start and end are not provided", () => {
    expect(fill([1, 2, 3], "_")).toEqual(["_", "_", "_"]);
  });

  test("does not fill any elements when start is equal to or greater than the array length", () => {
    expect(fill([1, 2], "*", 2, 3)).toEqual([1, 2]);
  });

  test("fills elements from start to end with the provided value", () => {
    expect(fill([1, 2, 3, 4, 5], "_", 1, -1)).toEqual([1, "_", "_", "_", 5]);
  });

  test("fills remaining elements with the provided value when end is not provided", () => {
    expect(fill([1, 2, 3], "_", 1)).toEqual([1, "_", "_"]);
  });
});

Solutions​

solution1.js
function fill(array, value, start = 0, end = array.length) {
    if (start < 0) {
        start = array.length + start;
    }

    if (end < 0) {
        end = array.length + end;
    }

    if (end > array.length) {
        end = array.length;
    }

    for (let i = start; i < end; i++) {
        array[i] = value;
    }

    return array;
}

export default inRange;