再帰を使用して JavaScript 配列値のすべての組み合わせを生成する方法

<code class="js">function allPossibleCases(arr) {
  if (arr.length === 0) {
    return [];
  } else if (arr.length === 1) {
    return arr[0];
  } else {
    var result = [];
    var allCasesOfRest = allPossibleCases(arr.slice(1));
    for (var i = 0; i < allCasesOfRest.length; i++) {
      for (var j = 0; j < arr[0].length; j++) {
        result.push(arr[0][j] + allCasesOfRest[i]);
      }
    }
    return result;
  }
}</code>

<code class="js">var first = ['a', 'b', 'c', 'd'];
var second = ['e'];
var third = ['f', 'g', 'h', 'i', 'j'];</code>

aef
aeg
aeh
aei
aej
bef
beg