Run TypeScript in Node without extensions

A couple of months ago I wrote about "Node watch mode and TypeScript" which suggests using the @swc-node/register package to be able to run node on .ts file without first converting it to .js using tsc.

In Node 22, you don't even need @swc-node/register. You can use --experimental-strip-types instead. (Note the prefix "experimental"). See release notes here.

Imagine a script like this:

// example.ts

function c2f(c: number) {
  return (c * 9) / 5 + 32;
}
console.log(c2f(123));

you can execute it directly in Node v22 using:

❯ node --experimental-strip-types --no-warnings example.ts
253.4

Pretty cool! In a real project, you'll want a tsconfig.json and some automation that checks that the types are correct. Mind you, if you use VS Code, it will automatically check basic TypeScript without a tsconfig.json file:

Benchmark

From the department of highly-unscientific-benchmarks-and-fruit-comparisons, let's test the execution speed of that sample example.ts using --experimental-strip-types versus --require @swc-node/register.

❯ node --version
v22.12.0

❯ hyperfine --warmup 3 \
  "node --require @swc-node/register example.ts" \
  "node --experimental-strip-types --no-warnings example.ts"
Benchmark 1: node --require @swc-node/register example.ts
  Time (mean ± σ):     141.1 ms ±   1.4 ms    [User: 128.9 ms, System: 14.4 ms]
  Range (min … max):   139.5 ms … 146.1 ms    19 runs

Benchmark 2: node --experimental-strip-types --no-warnings example.ts
  Time (mean ± σ):      53.9 ms ±   1.8 ms    [User: 53.5 ms, System: 6.6 ms]
  Range (min … max):    52.2 ms …  61.4 ms    52 runs

  Warning: Statistical outliers were detected. Consider re-running this benchmark on \
 a quiet system without any interferences from other programs. It might help to use the '--warmup' or '--prepare' options.

Summary
  node --experimental-strip-types --no-warnings example.ts ran
    2.62 ± 0.09 times faster than node --require @swc-node/register example.ts

See the "Summary" part. It claims that using --experimental-strip-types is 2.6x faster than --require @swc-node/register.
But this is not fair in terms of true runtime because in this benchmark, I suspect a large majority of the runtime time is the starting up of the Node process. However, if speed matters and your .ts file is small, here lies a chance to gain some speed.

Bonus benchmark

Deno and Bun can also run .ts files without extensions. Let's, for the fun of it, compare how fast it can start that execution:

❯ deno --version
deno 2.1.3 (stable, release, aarch64-apple-darwin)
v8 13.0.245.12-rusty
typescript 5.6.2

❯ bun --version
1.1.30

❯ hyperfine --warmup 3 \
  "node --require @swc-node/register example.ts" \
  "node --experimental-strip-types --no-warnings example.ts" \
  "bun run example.ts" \
  "deno run example.ts"
Benchmark 1: node --require @swc-node/register example.ts
  Time (mean ± σ):     143.8 ms ±   7.0 ms    [User: 130.5 ms, System: 14.9 ms]
  Range (min … max):   138.8 ms … 166.5 ms    20 runs

Benchmark 2: node --experimental-strip-types --no-warnings example.ts
  Time (mean ± σ):      55.6 ms ±   4.8 ms    [User: 54.0 ms, System: 7.1 ms]
  Range (min … max):    52.2 ms …  81.2 ms    45 runs

  Warning: Statistical outliers were detected. Consider re-running this benchmark on \
 a quiet system without any interferences from other programs. It might help to use the '--warmup' or '--prepare' options.

Benchmark 3: bun run example.ts
  Time (mean ± σ):       9.5 ms ±   0.8 ms    [User: 5.0 ms, System: 3.8 ms]
  Range (min … max):     8.1 ms …  13.1 ms    201 runs

Benchmark 4: deno run example.ts
  Time (mean ± σ):      23.5 ms ±  14.9 ms    [User: 14.5 ms, System: 7.2 ms]
  Range (min … max):    20.0 ms … 182.4 ms    119 runs

  Warning: Statistical outliers were detected. Consider re-running this benchmark on \
 a quiet system without any interferences from other programs. It might help to use the '--warmup' or '--prepare' options.

Summary
  bun run example.ts ran
    2.47 ± 1.57 times faster than deno run example.ts
    5.82 ± 0.70 times faster than node --experimental-strip-types --no-warnings example.ts
   15.06 ± 1.44 times faster than node --require @swc-node/register example.ts

Before focusing on the summary comparison, keep in mind that the mean time to run it is 143.8ms which is fast enough for executing scripts.