我目前正在处理 Eloquent JavaScript 的对象赋值,我想知道是否有任何方法可以在迭代器的 next()
方法中使用this
(请参阅代码)
class Group {
constructor() {
this.members = [];
}
add(member) {
if (this.has(member)) return;
this.members.push(member);
}
delete(member) {
if (!this.has(member)) return;
this.members.splice(this.members.indexOf(member), 1);
}
has(member) {
return this.members.indexOf(member) !== -1
}
static from(iterable) {
const group = new Group();
for (const element of iterable) {
group.add(element);
}
return group;
}
[Symbol.iterator]() {
let current = 0;
let last = this.members.length - 1;
const that = this;
return {
next() {
if (current <= last) {
return {
done: false,
value: that.members[current++]
}
} else return { done:true }
}
}
}
}
for (let value of Group.from(["a", "b", "c"])) {
console.log(value);
}
正如你所看到的,我正在使用这种奇怪的const that = this
模式。有什么办法可以摆脱它吗?除了使用箭头函数并将迭代器提取到单独的类,如解决方案中所示。
最排序的方式可能是在构造函数部分中实现对象的默认迭代器,并使用yield*
表达式委托给数组this.members
的另一个生成器。
constructor() {
this.members = [];
this[Symbol.iterator] = function* () {
yield* this.members;
}
}
class Group {
constructor() {
this.members = [];
this[Symbol.iterator] = function* () {
yield* this.members;
}
}
add(member) {
if (this.has(member)) return;
this.members.push(member);
}
delete(member) {
if (!this.has(member)) return;
this.members.splice(this.members.indexOf(member), 1);
}
has(member) {
return this.members.indexOf(member) !== -1
}
static from(iterable) {
const group = new Group();
for (const element of iterable) {
group.add(element);
}
return group;
}
}
for (let value of Group.from(["a", "b", "c"])) {
console.log(value);
}
.as-console-wrapper { max-height: 100% !important; top: 0; }
您可以使用箭头函数
class Group {
constructor() {
this.members = [];
}
add(member) {
if (this.has(member)) return;
this.members.push(member);
}
delete(member) {
if (!this.has(member)) return;
this.members.splice(this.members.indexOf(member), 1);
}
has(member) {
return this.members.indexOf(member) !== -1
}
static from(iterable) {
const group = new Group();
for (const element of iterable) {
group.add(element);
}
return group;
}
[Symbol.iterator]() {
let current = 0;
let last = this.members.length - 1;
return {
next: () => {
if (current <= last) {
return {
done: false,
value: this.members[current++]
}
} else return { done:true }
}
}
}
}
for (let value of Group.from(["a", "b", "c"])) {
console.log(value);
}