JavaScript Object valueOf & toString All In One

JavaScript Object valueOf & toString All In One

Object.prototype.valueOf() & Object.prototype.toString()

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/valueOf

The valueOf() method of Object instances converts the this value to an object. This method is meant to be overridden by derived objects for custom type conversion logic.

Object 實例的 valueOf() 方法將 this 值轉換爲對象。此方法旨在由派生對象重寫以實現自定義類型轉換邏輯。

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/toString

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/valueOf

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/toString

Instance methods

～https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/valueOf～ ❌

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/valueOf ✅

demos

class ArrayWrapper {
  arr: number[];
  constructor(nums: number[]) {
    this.arr = nums;
  }
  // ✅ 改寫 Object 內置方法 valueOf, 返回一個 number 整數 
  // ❓ object 相加 (本質上是 object 序列化後的 string 相加 ✅) => number 相加
  valueOf(): number {
    return this.arr.reduce((sum, i) => sum + i, 0);
  }
  // 序列化
  toString(): string {
    // return JSON.stringify(arr);
    return `[${this.arr.join(',')}]`;
  }
};



/**
 * const obj1 = new ArrayWrapper([1,2]);
 * const obj2 = new ArrayWrapper([3,4]);
 * obj1 + obj2; // 10
 * String(obj1); // "[1,2]"
 * String(obj2); // "[3,4]"
 */

https://leetcode.com/problems/array-wrapper/submissions/1258562707/?envType=study-plan-v2&envId=30-days-of-javascript

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