jsbuiltin

JavaScript's built-in operations for Go, as V8 and JavaScriptCore compute them: Number::toString, Number(string), parseInt, String.prototype toLowerCase / toUpperCase / trim and the whitespace set they share, UTF-16 length, slicing and ordering, TextDecoder('utf-8'), atob / btoa, encodeURIComponent / encodeURI, and the number JSON.parse makes of a JSON number.

import "github.com/trutohq/jsbuiltin"

jsbuiltin.FormatNumber(1e21)          // "1e+21"; 1e-7 is "1e-7", -0 is "0"
n, ok := jsbuiltin.ToNumber(" 0x1f ") // 31, true; "12abc" is NaN (ok false)
b, err := jsbuiltin.Atob("YQ")        // "a": forgiving-base64

The JSON value model ([[OwnPropertyKeys]] order, JSON.stringify bytes) is jsorder, which imports its number formatting from here. This module imports nothing of the org's, so jsorder can.

Why it exists

The owner's decision gotruto D-0868 (2026-10-30): each JavaScript runtime piece the Go ports need lives once, in a small module, held to the runtime by a harness. Before it, these operations had copies in gotruto, goenvoy and truto-jsonata-go that nothing compared: forgiving-base64 had four in gotruto and the module alone, the whitespace set six across the org.

Where the code came from

Moved, with its tests, on 2026-10-31. History stays in the source repositories.

here	from
number.go	jsorder number.go (b350e12); jsorder keeps AppendNumber / FormatNumber as wrappers
lowercase.go, utf16.go, textdecode.go, uri.go and their tests	truto-jsonata-go internal/jsonx (0492520), a copy of gotruto internal/jsonx at truto e5b134004
whitespace.go (IsWhiteSpace, Trim, ParseInt)	gotruto internal/qsx codec.go isJSWhitespace / parseIntJS and internal/jsonx IsJSSpace / Trim: one set, two copies, now one
tonumber.go	gotruto internal/qsx tonumber.go (via the module's internal/qs)
upper.go	truto-jsonata-go jsstring.go jsToUpperCase
base64.go	truto-jsonata-go fn_crypto.go atob (the one that tells Node's two errors apart); replaces gotruto's cursor.atob, analytics.atob, saml.atob, which accept and refuse the same strings
numbervalue.go	gotruto internal/jsonx NumberValue

Runtimes

The plain functions give V8's answers, as Node and workerd run it. Where Bun (JavaScriptCore, which runs Envoy) answers differently, an ...On function takes a Runtime: ToLowerCaseOn(RuntimeBun, s) leaves the 27 code points Unicode 16 gave a lowercase form as Bun 1.3.14 does, ToUpperCaseOn(RuntimeBun, s) leaves the 55 Unicode 16 and 17 uppercase additions likewise, and EncodeURIComponentOn / EncodeURIOn with RuntimeBun throw Bun's message, "String contained an illegal UTF-16 sequence.", where V8 says "URI malformed". TestBunContract holds them to testdata/bun/, which oracle/bun.mjs writes on Bun (make bun-goldens); its lowercase list is complete, so every code point it does not name must lower to itself.

How it is checked

Contract (make test): oracle/generate.mjs executes the runtime and writes every expected value under testdata/ (make goldens; testdata/runtime.json names the runtime: Node 24.18.1, V8 13.6, ICU 78.3, Unicode 17). TestContract compares 9,399 answers: 6,058 Number::toString (the same cases jsorder's generator writes), the whitespace set over every code point (as \s and as trim), toLowerCase / toUpperCase of every code point that maps and of context-sensitive strings, and Number, parseInt, atob, btoa, encodeURIComponent, encodeURI over edge cases. TextDecoder has its own golden (testdata/textdecode.ts).

The suite passes when exactly the lines in testdata/known-differences.txt differ; a new one fails it, and so does a listed one that stops differing. Today that is 29, all one cause (OPEN):

• Lowercase mapping of characters added in Unicode 16 and 17 (29 toLowerCase; e.g. U+A7CE, U+16EA0..U+16EB8). Node's ICU 78 maps them; the general path here is Go's unicode.ToLower, which leaves the Unicode 17 ones (unicode17Lowercase, matching workerd's Unicode 16). toUpperCase is x/text's cases, and since go.mod requires x/text v0.42.0 (2026-11-07) it maps the Unicode 16 and 17 uppercase forms as Node does. Before, the module required v0.21.0 (Unicode 15) while goenvoy and truto-jsonata-go built it at v0.42.0, so these tests ran on tables no consumer used. Bun 1.3.14 maps none of these: ToLowerCaseOn / ToUpperCaseOn with RuntimeBun (above) are held to it.

Watch (make watch, in make all): the generator runs again on Bun and on the installed Node, and TestWatch reports what differs into WATCH.txt without failing. 2026-10-31: Node 24.18.1, the 84 above; Bun 1.3.14, none.

Everything else (make all is fmt-check, vet, the race suite and the watch):

export PATH="$HOME/.local/go/bin:$PATH"
make all

Consumers

See HANDOFF.md.