JS ⟩ objects ⟩ Array ⟩ methods ⟩ sum(), average()
💾 replit: arr.sum()
// 🔸 arr.sum()
Array.prototype.sum = function(){
return this.reduce((result, value) => result + value, 0);
};
// 🔸 arr.average()
Array.prototype.average = function(){
return this.sum() / this.length;
};
💈範例：
[1,2,3].sum(), // 6
[].sum(), // 0
[1,2,3].average(), // 2