生成器对象是由一个 generator function 返回的,并且它符合可迭代协议和迭代器协议。
语法
function* gen() { yield 1; yield 2; yield 3; } let g = gen(); // "Generator { }"
方法
-
Generator.prototype.next()
-
返回一个由
yield
表达式生成的值。 -
Generator.prototype.return()
- 返回给定的值并结束生成器。
-
Generator.prototype.throw()
- 向生成器抛出一个错误。
示例
一个无限迭代器
function* idMaker(){ let index = 0; while(true) yield index++; } let gen = idMaker(); // "Generator { }" console.log(gen.next().value); // 0 console.log(gen.next().value); // 1 console.log(gen.next().value); // 2 // ...
传统的生成器对象
Firefox (SpiderMonkey) 在 JavaScript 1.7 中也实现了一个较早版本的生成器,其中函数声明中的星号(*)不是必需的 (只需在函数体中使用yield
关键字)。但是,旧式生成器已弃用。不要使用它们;他们将被删除 (bug 1083482)。
传统的生成器方法
-
Generator.prototype.next()
-
返回
yield
表达式产生的值. 与ES2015 生成器对象的 next()方法对应. -
Generator.prototype.close()
-
关闭生成器,因此执行该函数后调用
next()函数时将会抛出
StopIteration
错误. 与ES2015 生成器对象的 return()方法对应.. -
Generator.prototype.send()
-
用于将值发送到生成器。 该值由
yield
表达式返回, 并且返回下一个yield
表达式产生的值.send(x)
对应于ES2015生成器对象中的next(x)
-
Generator.
prototype.
throw()
- 向生成器抛出错误. 与ES2015 生成器对象的 throw()方法对应.
旧生成器对象示例
function fibonacci() { var a = yield 1; yield a * 2; } var it = fibonacci(); console.log(it); // "Generator { }" console.log(it.next()); // 1 console.log(it.send(10)); // 20 console.log(it.close()); // undefined console.log(it.next()); // throws StopIteration (as the generator is now closed)
规范
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) Generator objects |
Standard | Initial definition. |
ECMAScript Latest Draft (ECMA-262) Generator objects |
Draft |
浏览器兼容性
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out
https://github.com/mdn/browser-compat-data and send us a pull request.
Update compatibility data on GitHub
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Generator |
Chrome Full support 39 | Edge Full support 13 | Firefox Full support 26 | IE No support No | Opera Full support Yes | Safari Full support 10 | WebView Android Full support Yes | Chrome Android Full support 39 | Firefox Android Full support 26 | Opera Android Full support Yes | Safari iOS Full support 10 | Samsung Internet Android Full support Yes | nodejs Full support 4.0.0
|
next |
Chrome Full support 39 | Edge Full support 13 | Firefox Full support 26 | IE No support No | Opera Full support Yes | Safari Full support 10 | WebView Android Full support Yes | Chrome Android Full support 39 | Firefox Android Full support 26 | Opera Android Full support Yes | Safari iOS Full support 10 | Samsung Internet Android Full support Yes | nodejs Full support Yes |
return |
Chrome Full support 50 | Edge Full support 13 | Firefox Full support 38 | IE No support No | Opera Full support 37 | Safari Full support 10 | WebView Android Full support 50 | Chrome Android Full support 50 | Firefox Android Full support 38 | Opera Android Full support Yes | Safari iOS Full support 10 | Samsung Internet Android Full support 5.0 | nodejs Full support 6.0.0 |
throw |
Chrome Full support 39 | Edge Full support 13 | Firefox Full support 26 | IE No support No | Opera Full support Yes | Safari Full support 10 | WebView Android Full support Yes | Chrome Android Full support 39 | Firefox Android Full support 26 | Opera Android Full support Yes | Safari iOS Full support 10 | Samsung Internet Android Full support Yes | nodejs Full support 4.0.0
|
Legend
- Full support
- Full support
- No support
- No support
- User must explicitly enable this feature.
- User must explicitly enable this feature.
相关链接
Legacy generators
- The legacy generator function
- The legacy generator function expression
StopIteration
- The legacy Iterator protocol