05b22d2597
This commit introduces 4 changes:
1) Function declarations are wrapped using function declarations.
This has two advantages:
- We can rely on native hoisting, instead of using _blockHoist
- The function isn't wrapped until it is called. This avoids
problems where `regeneratorRuntime.wrap` was called before
that `babel-polyfill` was imported.
Example:
function fn() {}
// becomes
function fn() { return _fn.apply(this, arguments); }
function _fn() {
_fn = _wrapper(/* Original function ... */);
return _fn.apply(this, arguments);
}
2) Use a single template for both named and anonymous function
expressions. They already had the same behavior, but the one
used for named functions was a bit longer.
3) Use normal functions instead of arrow functions to wrap
function expressions.
4) Generate a name based on the original one for wrapped
functions (e.g. `foo` becomes `_foo` instead of `_ref`).
@babel/plugin-proposal-async-generator-functions
Turn async generator functions and for-await statements to ES2015 generators
Example
In
async function* agf() {
await 1;
yield 2;
}
Out
var _asyncGenerator = ...
let agf = (() => {
var _ref = _asyncGenerator.wrap(function* () {
yield _asyncGenerator.await(1);
yield 2;
});
return function agf() {
return _ref.apply(this, arguments);
};
})();
For await example
async function f() {
for await (let x of y) {
g(x);
}
}
Example Usage
async function* genAnswers() {
var stream = [ Promise.resolve(4), Promise.resolve(9), Promise.resolve(12) ];
var total = 0;
for await (let val of stream) {
total += await val;
yield total;
}
}
function forEach(ai, fn) {
return ai.next().then(function (r) {
if (!r.done) {
fn(r);
return forEach(ai, fn);
}
});
}
var output = 0;
forEach(genAnswers(), function(val) { output += val.value })
.then(function () {
console.log(output); // 42
});
Installation
npm install --save-dev @babel/plugin-proposal-async-generator-functions
Usage
Via .babelrc (Recommended)
.babelrc
{
"plugins": ["@babel/plugin-proposal-async-generator-functions"]
}
Via CLI
babel --plugins @babel/plugin-proposal-async-generator-functions script.js
Via Node API
require("@babel/core").transform("code", {
plugins: ["@babel/plugin-proposal-async-generator-functions"]
});