Hacker News new | ask | show | jobs
by cypher543 4367 days ago
It's consistent with the names of other type-checking functions. isNumber checks if a value is an instance of the Number class just like isDate checks if a value is an instance of the Date class. If it were isNumericType, they'd get questions about why the function doesn't follow the existing naming convention.

The only reason this is confusing for people is because they aren't familiar with IEEE 754 floating-point numbers and their representations. But since floats are used in almost every programming language, it's something that any programmer should be familiar with. Once they learn exactly what NaN means in that context, then the confusion should disappear.
2 comments
dragonwriter 4367 days ago
> The only reason this is confusing for people is because they aren't familiar with IEEE 754 floating-point numbers and their representations.

NaN is part of IEEE 754, but it is not a number.

The reason people are confused is because the JS datatype name has a small but critical disconnect from what the values it contains are.

link
xupybd 4367 days ago
I really dislike this sort of reasoning. That its only confusing because you don't know enough. It's possible to word things in ways that are easy to learn and lead you to an understanding of the underlying mechanics.

Its confusing because NaN explicitly states not a number. Then the function explicitly states is number.

However the two are in very different contexts, yet this is not communicated when using them. It's intuitive to think of a date as a class and there for the context is implicit in isDate. I don't think this is the case for isNumber.

I think this is less about people understanding floating-point numbers more about understanding that a function starting with is implies some form of type checking.

link
dragonwriter 4367 days ago
> Its confusing because NaN explicitly states not a number. Then the function explicitly states is number.

The problem is that "Number" is the name of a JS data type, and "number" is the name of a concept, the two don't match exactly, and when you are using camel-casing for word separation, you can't distinguish the two.

The function "isNumber" checks if the thing it is applied to is a JS Number, not if it is a number.

link