如何遍历平面JS数组，将其转换为嵌套的父/子结构？

function convertToNestedStructure(flatArray, parentId) {
  var nestedArray = [];
  for (var i = 0; i < flatArray.length; i++) {
    if (flatArray[i].parentId === parentId) {
      var children = convertToNestedStructure(flatArray, flatArray[i].id);
      if (children.length) {
        flatArray[i].children = children;
      }
      nestedArray.push(flatArray[i]);
    }
  }
  return nestedArray;
}

// 示例平面数组
var flatArray = [
  { id: 1, name: 'Parent 1', parentId: null },
  { id: 2, name: 'Child 1', parentId: 1 },
  { id: 3, name: 'Child 2', parentId: 1 },
  { id: 4, name: 'Grandchild 1', parentId: 2 },
  { id: 5, name: 'Parent 2', parentId: null },
];

var nestedArray = convertToNestedStructure(flatArray, null);
console.log(nestedArray);