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JavaScript JavaScript Basics (Retired) Creating Reusable Code with Functions Random Number Challenge, Part II Solution

Mark Bacolcol
Mark Bacolcol
7,354 Points
Posted by Mark Bacolcol
Mark Bacolcol
7,354 Points

Is "20" treated as a number?

A number within a string (isNaN("20")) runs false for me and the function returns an appropriate value. I tried using "20test" as a parameter and received an error as expected. So does JS treat strings with only numbers, as numbers?

2 Answers

Steven Parker
Steven Parker
231,271 Points
Steven Parker
Steven Parker
231,271 Points

This isNAN function performs a type coercion on the argument if it is not a number. Since "20" can be successfully converted to the value 20, it is tested as such.

If you want to test if something is not a number without coercion, try "if (typeof <myvalue> != "number)"

And if you are testing specifically for the value "NaN", you can use Number.isNaN() instead of plain isNaN()