Require isNaN() (use-isnan)

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. NaN has the unique property of not being equal to anything, including itself. That is to say, that the condition NaN !== NaN evaluates to true.

Rule Details

This rule is aimed at eliminating potential errors as the result of comparing against the special value NaN.

The following patterns are considered problems:

/*eslint use-isnan: 2*/

if (foo == NaN) { /*error Use the isNaN function to compare with NaN.*/
    // ...
}

if (foo != NaN) { /*error Use the isNaN function to compare with NaN.*/
    // ...
}

The following patterns are not considered problems:

/*eslint use-isnan: 2*/

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

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

Further reading

Version

This rule was introduced in ESLint 0.0.6.

Resources