noSelfCompare
Summary
Section titled “Summary”- Rule available since:
v1.0.0 - Diagnostic Category:
lint/suspicious/noSelfCompare - This rule is recommended, meaning it is enabled by default.
- This rule doesn’t have a fix.
- The default severity of this rule is error.
- Sources:
- Same as
no-self-compare - Same as
eq_op
- Same as
How to configure
Section titled “How to configure”{ "linter": { "rules": { "suspicious": { "noSelfCompare": "error" } } }}Description
Section titled “Description”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 “Examples”Invalid
Section titled “Invalid”if (x === x) {}code-block.js:1:5 lint/suspicious/noSelfCompare ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✖ This comparison uses the same expression on both sides.
> 1 │ if (x === x) {}
│ ^^^^^^^
2 │
ℹ Self-comparisons are usually redundant or a sign that the wrong value is being compared.
ℹ Compare two different values instead, or use Number.isNaN() if you are checking for NaN.
if (a.b.c() !== a.b .c()) {}code-block.js:1:5 lint/suspicious/noSelfCompare ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✖ This comparison uses the same expression on both sides.
> 1 │ if (a.b.c() !== a.b .c()) {}
│ ^^^^^^^^^^^^^^^^^^^^
2 │
ℹ Self-comparisons are usually redundant or a sign that the wrong value is being compared.
ℹ Compare two different values instead, or use Number.isNaN() if you are checking for NaN.
Related links
Section titled “Related links”Sponsored by
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