noGlobalIsNan

JavaScript (and super languages)

Summary

Rule available since: v1.0.0
Diagnostic Category: lint/suspicious/noGlobalIsNan
This rule is recommended, which means is enabled by default.
This rule has an unsafe fix.
The default severity of this rule is warning.

Description

Use Number.isNaN instead of global isNaN.

Number.isNaN() and isNaN() do not have the same behavior. When the argument to isNaN() is not a number, the value is first coerced to a number. Number.isNaN() does not perform this coercion. Therefore, it is a more reliable way to test whether a value is NaN.

Examples

Invalid

1
isNaN({}); // true

code-block.js:1:1 lint/suspicious/noGlobalIsNan  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ isNaN is unsafe. It attempts a type coercion. Use Number.isNaN instead.
  
  > 1 │ isNaN({}); // true
      │ ^^^^^
    2 │ 
  
  ℹ See the MDN documentation for more details.
  
  ℹ Unsafe fix: Use Number.isNaN instead.
  
    1   │ - isNaN({});·//·true
      1 │ + Number.isNaN({});·//·true
    2 2 │

Valid

1
Number.isNaN({}); // false

How to configure

1
{
2
  "linter": {
3
    "rules": {
4
      "suspicious": {
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        "noGlobalIsNan": "error"
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      }
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    }
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  }
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}