Iterator.from()
Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
Iterator.from()
静态方法从迭代器或可迭代对象创建新的 Iterator
对象。
¥The Iterator.from()
static method creates a new Iterator
object from an iterator or iterable object.
语法
参数
返回值
¥Return value
如果 object
是一个可迭代对象,则调用其 [Symbol.iterator]()
方法来获取迭代器。否则,object
被假定为迭代器。如果迭代器已经是 instanceof
Iterator
(这意味着它的原型链中有 Iterator.prototype
),则直接返回。否则,将创建一个新的 Iterator
对象来封装原始迭代器。
¥If object
is an iterable, its [Symbol.iterator]()
method is called to obtain the iterator. Otherwise, object
is assumed to be an iterator. If the iterator is already instanceof
Iterator
(which means it has Iterator.prototype
in its prototype chain), it is returned directly. Otherwise, a new Iterator
object is created that wraps the original iterator.
描述
¥Description
此方法用于将可能由库导出的自定义迭代器转换为 适当的迭代器。Iterator.from()
返回的所有迭代器对象都继承自一个公共原型对象,该对象具有以下方法:
¥This method exists to convert custom iterators, probably exported by libraries, to proper iterators. All iterator objects returned by Iterator.from()
inherit from a common prototype object, which has the following methods:
示例
将可迭代对象转换为适当的迭代器
¥Converting an iterable to a proper iterator
由于 obj
已经是一个可迭代对象,当调用 [Symbol.iterator]()
方法时,它会返回正确的迭代器,因此 Iterator.from(obj)
返回相同的迭代器。
¥Because obj
is already an iterable that returns a proper iterator when its [Symbol.iterator]()
method is called, Iterator.from(obj)
returns the same iterator.
const iterator = (function* () {
yield 1;
yield 2;
yield 3;
})();
const obj = {
[Symbol.iterator]() {
return iterator;
},
};
const iterator2 = Iterator.from(obj);
console.log(iterator2 === iterator); // true
因为 obj2
是一个迭代器,当调用 [Symbol.iterator]()
方法时,它会返回一个非正确的迭代器,所以 Iterator.from(obj2)
返回一个封装原始迭代器的新迭代器。
¥Because obj2
is an iterable that returns a non-proper iterator when its [Symbol.iterator]()
method is called, Iterator.from(obj2)
returns a new iterator that wraps the original iterator.
const iterator = {
current: 0,
next() {
return { value: this.current++, done: false };
},
};
const obj2 = {
[Symbol.iterator]() {
return iterator;
},
};
const iterator2 = Iterator.from(obj2);
console.log(iterator2 === iterator); // false
console.log(iterator2.next()); // { value: 0, done: false }
console.log(iterator.next()); // { value: 1, done: false }
将迭代器转换为适当的迭代器
¥Converting an iterator to a proper iterator
因为 obj
已经是一个正确的迭代器,所以 Iterator.from(obj)
返回其自身。
¥Because obj
is already a proper iterator, Iterator.from(obj)
returns itself.
const obj = (function* () {
yield 1;
yield 2;
yield 3;
})();
const iterator = Iterator.from(obj);
console.log(iterator === obj); // true
因为 obj2
是一个非正确迭代器,所以 Iterator.from(obj2)
返回一个封装原始迭代器的新迭代器。
¥Because obj2
is a non-proper iterator, Iterator.from(obj2)
returns a new iterator that wraps the original iterator.
const obj2 = {
current: 0,
next() {
return { value: this.current++, done: false };
},
};
const iterator = Iterator.from(obj2);
console.log(iterator === obj2); // false
console.log(iterator.next()); // { value: 0, done: false }
console.log(obj2.next()); // { value: 1, done: false }
规范
Specification |
---|
Iterator Helpers # sec-iterator.from |