ts-check-perf

A tool for measuring and comparing type-checking speed of TS samples.

npm i -D ts-check-perf

It runs TS type-checked many times over the same samples to measure type-checking performance.

Importing modules into samples

As long as you have "skipLibCheck": true in tsconfig.json, importing external modules won't take time of measurement.

Such benchmark case will only measure type-checking of Partial<Type>:

import { Type } from 'external-module'

export type P = Partial<Type>

But, unfortunately, the same does not work for local files, and such benchmark doesn't make sense:

import { Type } from './my-code'

export type P = Partial<Type>

It will mostly measure time of type-checking of imported file.

Defining samples

For example, we want to know which is faster: extending type with new properties, or interface.

Define a common code that is not wanted to be measured as a preparation:

const preparation = `
  type Type = {
    one: 1
    two: 2
    three: 3
  }
  
  interface Interface = {
    one: 1
    two: 2
    three: 3
  }
`;

Note that preparation usefulness is very limited, and most likely you won't need it in your benchmarks. It can be used to define types that somehow gets available in samples below, but it cannot define variables in a same way, it cannot be imported into samples, and when you import external module into preparation it also most likely won't work as expected. But, it works for this use-case.

Next, we can define our samples, one will extend the type, and the second will extend the interface.

Types in samples must be exported, otherwise TS compiler will throw an error about name collision.

Sample code can be defined as object where keys are sample names and values are TS code:

const samples = {
  type: `
    export type Extended = Type & {
      four: 4
      five: 5
      six: 6
    }
  `,
  interface: `
    export interface Extended extends Interface {
      four: 4
      five: 5
      six: 6
    }
  `,
};

Or, samples can be defined as array, samples names will be 1st, 2nd, 3rd:

const samples = [
  `
    export type Extended = Type & {
      four: 4
      five: 5
      six: 6
    }
  `,
  `
    export interface Extended extends Interface {
      four: 4
      five: 5
      six: 6
    }
  `,
];

Measure time

measureTime type checks first sample, second, first, second, and does so 1000 times for each sample.

import { measureTime } from "ts-check-perf";

measureTime({
  preparation,
  samples,
})

Outputs:

1st.ts (slowest): 35ms
2nd.ts +1.06x (fastest): 33ms

Measurement numbers below 1 second should not be trusted, such results will be different on every benchmark run. Changing it to type-check million times:

measureTime({
  runTimes: 1_000_000,
  preparation,
  samples,
})

1st.ts (slowest): 2899ms
2nd.ts +1.22x (fastest): 2385ms

Measure speed

measureTime type checks first sample, second, first, second, and continues for 100ms for each sample, measuring how many operations per second each sample gives.

import { measureSpeed } from "ts-check-perf";

measureSpeed({
  preparation,
  samples,
})

1st.ts (slowest): 289k ops/s
2nd.ts +1.4x (fastest): 404.1k ops/s

Change the duration by setting durationMs:

measureSpeed({
  durationMs: 1000,
  preparation,
  samples,
})

1st.ts (slowest): 332.4k ops/s
2nd.ts +1.37x (fastest): 454.9k ops/s

benchmark.js

You can use ts-check-perf in together with other benchmarking tools which provides more metrics.

import { setupTsBenchmark } from "ts-check-perf";
import * as Benchmark from 'benchmark'

const { typeChecker, sourceFiles } = setupTsBenchmark({
  preparation,
  samples,
})

const suite = new Benchmark.Suite()

suite
  .add('type', () => {
    typeChecker.checkFileForBenchmark(sourceFiles[0]);
  })
  .add('interface', () => {
    typeChecker.checkFileForBenchmark(sourceFiles[1]);
  })
  .on('cycle', (e) => {
    console.log(String(e.target));
  })
  .on('complete', () => {
    console.log('Fastest is ' + suite.filter('fastest').map('name').join(', '));
  })
  .run()

type x 349,530 ops/sec ±6.94% (74 runs sampled)
interface x 286,340 ops/sec ±17.00% (63 runs sampled)
Fastest is type

Common parameters

Set log: false to measureTime and measureSpeed to disable logging, they return a result Record<'sample name', number> you can use programmatically.

By default, this tool is looking for tsconfig.json for configuring TS, you can change this file name by setting tsconfigName parameter to options of measureTime, measureSpeed, setupTsBenchmark.

ESM

This tools works by patching TS source code on-the-fly: it reads TypeScript's compiler code from node_modules, injects own function into it, and saves the result to require.cache.

Such trick only works with CommonJS module system, there is no official way to do this for ESM, so this library doesn't support ESM and have no plans for it.

Bun

Interesting observation, running the example from above with measureSpeed:

$ node -v
v20.8.1
$ node bench.js
1st.ts (slowest): 323.5k ops/s
2nd.ts +1.27x (fastest): 412.1k ops/s

Running the same file with Bun:

$ bun -v
1.0.15
$ bun bench.js
1st.ts (slowest): 562.0k ops/s
2nd.ts +1.12x (fastest): 631.9k ops/s