V7011. Comparison with 'NaN' is incorrect. Use 'isNaN()' or 'Number.isNaN()' method instead.

The analyzer detected that a value is compared with NaN using a binary operator. Since NaN in JavaScript is implemented according to the IEEE 754 standard, comparisons with NaN that use == or ===operators always return false. Most likely, such a comparison in the code is a mistake.

The example:

let a = NaN;
console.log(a == NaN);  // false
console.log(a === NaN); // false

let b = "10"
console.log(b ==  NaN); // false
console.log(b === NaN); // false

The check always returns false, no matter which value is compared with NaN. If the != or !== operator is used for comparison, the result is always true.

To check whether a value is NaN, use special methods isNaN() and Number.isNaN().

The fixed example:

let a = NaN;
console.log(isNaN(a));        // true
console.log(Number.isNaN(a)); // true

let b = "10"
console.log(isNaN(b)); // false
Number.isNaN(b);       // false

Note the difference between these two methods in the example below.

The isNaN() method returns true if the checked value is equal to NaN or becomes NaN after its conversion to a number. The Number.isNaN() method does not convert the checked value to a number.

The example:

console.log(isNaN("value"));        // true
console.log(Number.isNaN("value")); // false

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