feat: return self when num === 0

[li-jia-nan]

No description provided.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (0fd28cc) 95.23% compared to head (27be576) 95.23%.

❗ Current head 27be576 differs from pull request most recent head 440d46b. Consider uploading reports for the commit 440d46b to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             next     #158   +/-   ##
=======================================
  Coverage   95.23%   95.23%           
=======================================
  Files          28       28           
  Lines        2561     2561           
  Branches      388      389    +1     
=======================================
  Hits         2439     2439           
  Misses        122      122           

Files	Coverage Δ
src/util/index.ts	64.32% <100.00%> (ø)

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