Salesforce JS-Dev-101 Exam - Topic 1 Question 8 Discussion

Comprehensive and Detailed Explanation From Exact Extract JavaScript knowledge:

We already know NaN is special: it is not equal to itself.

Check each:

A . value === Number.NaN

Number.NaN is NaN.

NaN === NaN is always false.

This will never be true; cannot reliably detect NaN.

B . value == NaN

NaN == NaN is also always false.

Again, this never detects NaN.

C . isNaN(value)

Global isNaN converts its argument to a number and then checks if the result is NaN.

This can detect NaN, but it may also return true for non-number values that coerce to NaN, such as isNaN('foo').

Regardless, it is a standard way to detect if a value is ''NaN-like'' in JavaScript.

D . Object.is(value, NaN)

Object.is(NaN, NaN) returns true.

This is a strict way to detect a value that is exactly NaN (no coercion).

Therefore, among the given choices, the two viable ways to detect NaN are:

isNaN(value)

Object.is(value, NaN)

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