Membina rentetan daripada matriks aksara dan tatasusunan angka dalam JavaScript

[
   [‘a’, ‘b’, ‘c’, d’],
   [‘o’, ‘f’, ‘r’, ‘g’],
   [‘h’, ‘i’, ‘e’, ‘j’],
   [‘k’, ‘l’, ‘m’, n’]
];

[1, 4, 5, 7, 11]

const arr = [
   ['a', 'b', 'c', 'd'],
   ['o', 'f', 'r', 'g'],
   ['h', 'i', 'e', 'j'],
   ['k', 'l', 'm', 'n']
];
const pos = [1, 4, 5, 7, 11];
const buildString = (arr = [], pos = []) => {
   const flat = [];
   arr.forEach(sub => {
      flat.push(...sub);
   });
   let res = '';
   pos.forEach(num => {
      res += (flat[num - 1] || '');
   });
   return res;
};
console.log(buildString(arr, pos));

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