[sarathfrancis90]

Summary

compat/size returns the number of own enumerable keys for array-like objects, so it diverges from lodash for values that have a valid length but aren't real arrays:

import { size } from 'es-toolkit/compat';
import _ from 'lodash';

size({ length: 3 });             // 1   (expected 3)
_.size({ length: 3 });           // 3

size({ 0: 'a', 1: 'b', length: 2 }); // 3   (expected 2)
_.size({ 0: 'a', 1: 'b', length: 2 }); // 2

lodash's size checks isArrayLike(collection) first and returns collection.length for array-like values, only falling back to the own-key count for plain objects. es-toolkit skipped that check and went straight to Object.keys(target).length.

Fix

Route array-like values through isArrayLike and return their length, matching lodash. Objects whose length is not a valid array length (negative, fractional, non-number, or above MAX_SAFE_INTEGER) are still not treated as array-like and fall back to the own-key count, exactly as before — the existing size tests covering those cases keep passing.

Arrays, strings, and arguments objects are unaffected (they were already array-like and produced the same result). Maps and Sets are not array-like, so they still return .size.

Tests

Added cases asserting array-like objects are counted by length. The new tests fail on main and pass with the fix. The full src/compat suite (3093 tests), tsc --noEmit, and lint all pass.

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Project	Deployment	Actions	Updated (UTC)
es-toolkit	Ready	Preview, Comment	Jun 12, 2026 3:50am

[raon0211]

Thanks!