noSelfCompare (since v1.0.0)
Diagnostic Category: lint/suspicious/noSelfCompare
Sources:
- Same as:
no-self-compare - Same as:
eq_op
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 usetypeof 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 ExamplesInvalid
Section titled Invalidif (x === x) {}code-block.js:1:5 lint/suspicious/noSelfCompare ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✖ Comparing to itself is potentially pointless.
> 1 │ if (x === x) {}
│ ^^^^^^^
2 │
if (a.b.c() !== a.b .c()) {}code-block.js:1:5 lint/suspicious/noSelfCompare ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✖ Comparing to itself is potentially pointless.
> 1 │ if (a.b.c() !== a.b .c()) {}
│ ^^^^^^^^^^^^^^^^^^^^
2 │