early break reduce()

💈範例

codepen ⟩ early break reduce()?

const {log} = console;

//                0        1          2          3
const array = ['apple', '-pen', '-pineapple', '-pen'];

// early break reduce()
const x = array  
  .slice(0)                           // ⭐️ copy of "array"             
  .reduce((acc, curr, i, arr) => {
      if (i === 2) arr.splice(i+1);   // ⭐️ eject early by mutating `arr` 
      return (acc += curr);           //   (array copy)
  }, '');

log(x);                               // "apple-pen-pineapple"

📘 手冊

• Array.prototype ⟩

  • .reduce()

  • .slice() - 擷取某一段，產生新陣列。

  • .splice() - 截斷原陣列、插入新元素。(⭐️ 注意：會回傳「被截掉的部分」❗️)

📗 參考

• JS.info ⟩ reduce(), reduceRight()

🗣 討論

• How to early break reduce() method?