javascript - 在 ES6 中使链表可迭代

Question

我有一个 JavaScript 链接列表，我需要使用 for of 循环使其可迭代。我几乎完成了，但似乎没有办法获得结果中包含的第一个值。这是一个简化版本:

var obj = {value: 1, next: {value: 2, next: {value: 3, next: {value: 4, next: {value: 5, next: {value: 6, next: {value:7, next: null}}}}}}};

obj[Symbol.iterator] = function() {
  var current = this;
  return {
    next() {
      if (current.next !== null) {
        current = current.next;
        return {value: current.value, done: false};
      }
      return {done: true}
    }
  }
}

for (const x of obj) {
  console.log(x)
}

// this is how you get the values printed with no loop
// console.log(obj.value + '->' + obj.next.value + '->' + obj.next.next.value)

Answer 1

问题是您在检索 value 之前将 current 移动到下一个节点。

var obj = {value: 1, next: {value: 2, next: {value: 3, next: {value: 4, next: {value: 5, next: {value: 6, next: {value:7, next: null}}}}}}};

obj[Symbol.iterator] = function() {
  var current = this;
  return {
    next() {
      if (current) {
        var value = current.value;
        current = current.next;
        return {value: value, done: false};
      }
      return {done: true};
    }
  };
};

for (const x of obj) {
  console.log(x);
}

用 generator function 实现迭代器要容易得多.

var obj = {value: 1, next: {value: 2, next: {value: 3, next: {value: 4, next: {value: 5, next: {value: 6, next: {value:7, next: null}}}}}}};

obj[Symbol.iterator] = function*() {
  var current = this;
  while (current) {
    yield current.value;
    current = current.next;
  }
};

for (const x of obj) {
  console.log(x);
}