fix(@stdlib/string/base/atob): guard against missing global atob

[Planeshifter]

Description

This pull request:

• fixes a ReferenceError: atob is not defined in @stdlib/string/base/atob on Node.js versions lacking the global atob (<16). lib/global.js bare-referenced atob, which throws at module-load time. Since lib/index.js requires ./main.js (and transitively ./global.js) unconditionally before running its hasAtobSupport() feature detection, this crashed require('@stdlib/string/base/atob') outright on Node.js <16, not just in tests.
• guards the reference with typeof atob === 'function', which does not throw on an undeclared identifier, matching the existing pattern in @stdlib/assert/has-atob-support/lib/atob.js. On unsupported platforms, the module now resolves to null, and the existing try/catch in main.js plus the hasAtobSupport() check in index.js handle the rest as originally intended.

Related Issues

None.

Questions

No.

Other

Failing run: https://github.com/stdlib-js/stdlib/actions/runs/28736797063 (linux_test, jobs "Node.js v12" and "Node.js v14")

Symptom: ReferenceError: atob is not defined at lib/node_modules/@stdlib/string/base/atob/lib/global.js:23:18, thrown from test/test.main.js on require, before tape's skip option ever takes effect.

Root cause: bare (unguarded) reference to the global atob in global.js, executed unconditionally at module load via index.js → main.js → global.js, regardless of the package's own hasAtobSupport() feature detection.

Validation: confirmed via manual node -e runs that (1) requiring lib/main.js with globalThis.atob deleted no longer throws and now returns null on invocation, (2) requiring lib/index.js in the same simulated environment correctly falls back to the polyfill and returns the correct decoded string, (3) normal behavior on a Node.js version with native atob is unchanged. A full node_modules install was not available in this environment to run the package's tape suite directly. Reviewed independently by three agents (correctness, regression scope, style/conventions) — all approved, no blocking findings.

Checklist

• Read, understood, and followed the contributing guidelines.

AI Assistance

• Yes

• No

• Code generation (e.g., when writing an implementation or fixing a bug)

• Test/benchmark generation

• Documentation (including examples)

• Research and understanding

Disclosure

This PR was authored by Claude Code as part of an automated CI-failure investigation routine: it identified the failing nightly job, root-caused the ReferenceError, applied the fix, and validated it against three independent review passes before opening this draft.

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@stdlib-js/reviewers

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Generated by Claude Code

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
string/base/atob	$\\color{green}217/217$ $\\color{green}+100.00\\%$	$\\color{red}11/12$ $\\color{green}+91.67\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}217/217$ $\\color{green}+100.00\\%$

The above coverage report was generated for the changes in this PR.