require calls to isNaN()
when checking for NaN
(use-isnan)
The "extends": "eslint:recommended"
property in a configuration file enables this rule.
In JavaScript, NaN
is a special value of the Number
type. It's used to represent any of the "not-a-number" values represented by the double-precision 64-bit format as specified by the IEEE Standard for Binary Floating-Point Arithmetic.
Because NaN
is unique in JavaScript by not being equal to anything, including itself, the results of comparisons to NaN
are confusing:
NaN === NaN
orNaN == NaN
evaluate to falseNaN !== NaN
orNaN != NaN
evaluate to true
Therefore, use Number.isNaN()
or global isNaN()
functions to test whether a value is NaN
.
Rule Details
This rule disallows comparisons to 'NaN'.
Examples of incorrect code for this rule:
/*eslint use-isnan: "error"*/
if (foo == NaN) {
// ...
}
if (foo != NaN) {
// ...
}
Examples of correct code for this rule:
/*eslint use-isnan: "error"*/
if (isNaN(foo)) {
// ...
}
if (!isNaN(foo)) {
// ...
}
Version
This rule was introduced in ESLint 0.0.6.