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https://github.com/mcollina/typescript-async-await-target-cost
https://github.com/mcollina/typescript-async-await-target-cost
Last synced: about 1 month ago
JSON representation
- Host: GitHub
- URL: https://github.com/mcollina/typescript-async-await-target-cost
- Owner: mcollina
- License: mit
- Created: 2022-03-11T13:23:54.000Z (almost 3 years ago)
- Default Branch: main
- Last Pushed: 2022-03-15T00:06:39.000Z (almost 3 years ago)
- Last Synced: 2024-11-01T12:42:26.699Z (about 2 months ago)
- Language: Shell
- Size: 5.86 KB
- Stars: 26
- Watchers: 3
- Forks: 4
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# typescript-async-await-target-cost
This project aims to benchmark the cost of an await in TypeScript with different targets.
__TL;DR set at least es2017 as a target.__
## The file
```typescript
async function empty () {
return true
}
async function loop () {
console.time('loop')
for (let i = 0; i < 1000000; i++) {
await empty
}
console.timeEnd('loop')
}
loop()
```
## The Results
```
benchmarking async/await with TS default target es3
loop: 144.375ms
------------------------------------------------------
benchmarking async/await with TS target es2015
loop: 153.384ms
------------------------------------------------------
benchmarking async/await with TS target es2016
loop: 111.933ms
------------------------------------------------------
benchmarking async/await with TS target es2017
loop: 96.598ms
------------------------------------------------------
benchmarking async/await with TS target es2018
loop: 97.948ms
------------------------------------------------------
benchmarking async/await with TS target esnext
loop: 97.288ms
```
## Why
If we are not setting the target in TypeScript, the code is compiled in es3.
Therefore the compiler uses the following to run each promise:
```javascript
var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
return new (P || (P = Promise))(function (resolve, reject) {
function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
step((generator = generator.apply(thisArg, _arguments || [])).next());
});
};
var __generator = (this && this.__generator) || function (thisArg, body) {
var _ = { label: 0, sent: function() { if (t[0] & 1) throw t[1]; return t[1]; }, trys: [], ops: [] }, f, y, t, g;
return g = { next: verb(0), "throw": verb(1), "return": verb(2) }, typeof Symbol === "function" && (g[Symbol.iterator] = function() { return this; }), g;
function verb(n) { return function (v) { return step([n, v]); }; }
function step(op) {
if (f) throw new TypeError("Generator is already executing.");
while (_) try {
if (f = 1, y && (t = op[0] & 2 ? y["return"] : op[0] ? y["throw"] || ((t = y["return"]) && t.call(y), 0) : y.next) && !(t = t.call(y, op[1])).done) return t;
if (y = 0, t) op = [op[0] & 2, t.value];
switch (op[0]) {
case 0: case 1: t = op; break;
case 4: _.label++; return { value: op[1], done: false };
case 5: _.label++; y = op[1]; op = [0]; continue;
case 7: op = _.ops.pop(); _.trys.pop(); continue;
default:
if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }
if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }
if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }
if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }
if (t[2]) _.ops.pop();
_.trys.pop(); continue;
}
op = body.call(thisArg, _);
} catch (e) { op = [6, e]; y = 0; } finally { f = t = 0; }
if (op[0] & 5) throw op[1]; return { value: op[0] ? op[1] : void 0, done: true };
}
};
function empty() {
return __awaiter(this, void 0, void 0, function () {
return __generator(this, function (_a) {
return [2 /*return*/, true];
});
});
}
function loop() {
return __awaiter(this, void 0, void 0, function () {
var i;
return __generator(this, function (_a) {
switch (_a.label) {
case 0:
console.time('loop');
i = 0;
_a.label = 1;
case 1:
if (!(i < 1000000)) return [3 /*break*/, 4];
return [4 /*yield*/, empty];
case 2:
_a.sent();
_a.label = 3;
case 3:
i++;
return [3 /*break*/, 1];
case 4:
console.timeEnd('loop');
return [2 /*return*/];
}
});
});
}
loop();
```
As you can imagine the code is significantly more expensive to run than the internal implementation of V8.