I was exploring the includes() function and stumbled upon this interesting code snippet:
[NaN].includes(NaN) //Returns trueHowever,
NaN === NaN // Returns false
How can this discrepancy be explained?
I was exploring the includes() function and stumbled upon this interesting code snippet:
[NaN].includes(NaN) //Returns trueHowever,
NaN === NaN // Returns false
How can this discrepancy be explained?
When we compare NaN === NaN and use the includes method like [NaN].includes(NaN), we are essentially posing two distinct questions:
The entity NaN is shapeless, denoting an absence of numeric value, making it impossible to conduct a direct comparison. The Equality operation adheres to the Strict Equality Comparison guidelines and asserts that any evaluation involving x === y where NaN features on either side will invariably yield false:
a. If x is NaN, return false.
b. If y is NaN, return false.
Yet, in order to locate a NaN within an array while adhering to the Array#includes' requirement of a single parameter sans callback function, we must assign a "name" to our sought-after element. This necessity stems from the specification outlined in the ECMAScript 2016 (ECMA-262) documentation:
The includes method deviates from indexOf by employing the SameValueZero algorithm rather than Strict Equality Comparison, facilitating the identification of NaN array elements. Furthermore, it treats missing array elements as undefined instead of skipping over them.
The protocol delineated in SameValueZero(x, y) dictates that during comparison:
If both x and y resolve to NaN, the result is true.
Check out this link for more information on NaN in JavaScript.
When it comes to NaN in JavaScript, using the equality operators (== and ===) can be tricky as they do not accurately determine if a value is NaN or not. This is why the isNaN function comes into play.
[ NaN ].includes(NaN) This code snippet checks if the value NaN is present in the array [ ].
Both NaN === NaN and NaN == NaN will return false. The includes method simply verifies if a value exists within the array it is called on, possibly using the typeof() function under the hood.
typeof(NaN) // number
[ NaN ].includes(NaN) // true
typeof("1") // string
[ 1 ].includes("1") // false
typeof(1) // number
[ 1 ].includes(1) // true
This behavior follows the SameValueZero Algorithm defined for the includes method, where type checking is internally performed.
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