108 lines
2.5 KiB
Markdown
108 lines
2.5 KiB
Markdown
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# babel-plugin-transform-async-generator-functions
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> Turn async generator functions and for-await statements to ES2015 generators
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## Example
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**In**
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```javascript
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async function* agf() {
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await 1;
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yield 2;
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}
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```
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**Out**
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```javascript
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var _asyncGenerator = ...
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let agf = (() => {
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var _ref = _asyncGenerator.wrap(function* () {
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yield _asyncGenerator.await(1);
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yield 2;
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});
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return function agf() {
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return _ref.apply(this, arguments);
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};
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})();
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```
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For await example
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```js
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async function f() {
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for await (let x of y) {
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g(x);
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}
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}
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```
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**Example Usage**
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```js
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async function* genAnswers() {
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var stream = [ Promise.resolve(4), Promise.resolve(9), Promise.resolve(12) ];
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var total = 0;
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for await (let val of stream) {
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total += await val;
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yield total;
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}
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}
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function forEach(ai, fn) {
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return ai.next().then(function (r) {
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if (!r.done) {
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fn(r);
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return forEach(ai, fn);
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}
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});
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}
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var output = 0;
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forEach(genAnswers(), function(val) { output += val.value })
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.then(function () {
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console.log(output); // 42
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});
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```
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[Try it Out in the REPL](https://babeljs.io/repl/#?babili=false&evaluate=true&lineWrap=false&presets=stage-3&code=async%20function*%20genAnswers()%20%7B%0A%20%20var%20stream%20%3D%20%5B%20Promise.resolve(4)%2C%20Promise.resolve(9)%2C%20Promise.resolve(12)%20%5D%3B%0A%20%20var%20total%20%3D%200%3B%0A%20%20for%20await%20(let%20val%20of%20stream)%20%7B%0A%20%20%20%20total%20%2B%3D%20await%20val%3B%0A%20%20%20%20yield%20total%3B%0A%20%20%7D%0A%7D%0A%0Afunction%20forEach(ai%2C%20fn)%20%7B%0A%20%20return%20ai.next().then(function%20(r)%20%7B%0A%20%20%20%20if%20(!r.done)%20%7B%0A%20%20%20%20%20%20fn(r)%3B%0A%20%20%20%20%20%20return%20forEach(ai%2C%20fn)%3B%0A%20%20%20%20%7D%0A%20%20%7D)%3B%0A%7D%0A%0Avar%20output%20%3D%200%3B%0AforEach(genAnswers()%2C%20function(val)%20%7B%20output%20%2B%3D%20val.value%20%7D)%0A.then(function%20()%20%7B%0A%20%20console.log(output)%3B%20%2F%2F%2042%0A%7D)%3B&experimental=true&loose=false&spec=false&playground=true&stage=0)
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## Installation
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```sh
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npm install --save-dev babel-plugin-transform-async-generator-functions
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```
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## Usage
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### Via `.babelrc` (Recommended)
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**.babelrc**
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```json
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{
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"plugins": ["transform-async-generator-functions"]
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}
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```
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### Via CLI
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```sh
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babel --plugins transform-async-generator-functions script.js
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```
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### Via Node API
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```javascript
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require("babel-core").transform("code", {
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plugins: ["transform-async-generator-functions"]
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});
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```
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## References
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* [Proposal: Asynchronous iteration for ECMAScript](https://github.com/tc39/proposal-async-iteration)
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