use-isnan

NOTE: this rule is part of the recommended rule set.

Enable full set in deno.json:

{
  "lint": {
    "rules": {
      "tags": ["recommended"]
    }
  }
}

Enable full set using the Deno CLI:

deno lint --rules-tags=recommended

This rule can be explictly included to or excluded from the rules present in the current tag by adding it to the include or exclude array in deno.json:

{
  "lint": {
    "rules": {
      "include": ["use-isnan"],
      "exclude": ["use-isnan"]
    }
  }
}

Disallows comparisons to NaN.

Because NaN is unique in JavaScript by not being equal to anything, including itself, the results of comparisons to NaN are confusing:

NaN === NaN or NaN == NaN evaluate to false
NaN !== NaN or NaN != NaN evaluate to true

Therefore, this rule makes you use the isNaN() or Number.isNaN() to judge the value is NaN or not.

Invalid:

if (foo == NaN) {
  // ...
}

if (foo != NaN) {
  // ...
}

switch (NaN) {
  case foo:
    // ...
}

switch (foo) {
  case NaN:
    // ...
}

Valid:

if (isNaN(foo)) {
  // ...
}

if (!isNaN(foo)) {
  // ...
}

use-isnan

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