refactor: replace deprecated String.prototype.substr() with substring()#2181
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trekhleb merged 2 commits intoJun 14, 2026
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String.prototype.substr() is deprecated and may be removed in future JavaScript engine versions (Annex B of the ECMAScript specification). Replaced all occurrences in the codebase with String.prototype.substring(): - src/algorithms/string/rabin-karp/rabinKarp.js - src/algorithms/cryptography/polynomial-hash/__test__/SimplePolynomialHash.test.js - src/algorithms/cryptography/polynomial-hash/__test__/PolynomialHash.test.js The behavior is identical since all substr(start, length) calls are converted to substring(start, start + length) with the same arguments. All existing tests pass.
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Problem
String.prototype.substr()is a legacy feature defined in Annex B of the ECMAScript specification and is deprecated. It may be removed from future JavaScript engine versions.The codebase uses
substr()in 5 places across 3 files.Fix
Replaced all
substr(start, length)calls withsubstring(start, start + length), which is the modern, standard alternative. The behavior is identical for all cases in this codebase.Files changed:
src/algorithms/string/rabin-karp/rabinKarp.js— source codesrc/algorithms/cryptography/polynomial-hash/__test__/SimplePolynomialHash.test.js— testsrc/algorithms/cryptography/polynomial-hash/__test__/PolynomialHash.test.js— testConversion pattern:
All 7 affected tests pass.