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noSelfCompare (since v1.0.0)

Diagnostic Category: lint/suspicious/noSelfCompare

Sources:

Disallow comparisons where both sides are exactly the same.

Comparing a variable against itself is usually an error, either a typo or refactoring error. It is confusing to the reader and may potentially introduce a runtime error.

The only time you would compare a variable against itself is when you are testing for NaN. However, it is far more appropriate to use typeof x === 'number' && Number.isNaN(x) for that use case rather than leaving the reader of the code to determine the intent of self comparison.

Examples

Section titled Examples

Invalid

Section titled Invalid
if (x === x) {}
suspicious/noSelfCompare.js:1:5 lint/suspicious/noSelfCompare ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Comparing to itself is potentially pointless.
  
  > 1 │ if (x === x) {}
      │     ^^^^^^^
    2 │ 
  

if (a.b.c() !== a.b .c()) {}
suspicious/noSelfCompare.js:1:5 lint/suspicious/noSelfCompare ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Comparing to itself is potentially pointless.
  
  > 1 │ if (a.b.c() !== a.b .c()) {}
      │     ^^^^^^^^^^^^^^^^^^^^
    2 │
Section titled Related links