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

Lynn Mitchell
Lynn Mitchell
5,133 Points
Posted by Lynn Mitchell
Lynn Mitchell
5,133 Points

Why is it that you don't have to say if (isNAN(upper) = true )?

Why is it that you don't have to say if (isNAN(upper) = true )? I tried to run this with

function getRandomNumber( lower, upper ) { if (isNAN(upper) =true || isNAN(lower) = true{ throw new Error("You must enter a number!"); }else{ return Math.floor(Math.random() * (upper - lower + 1)) + lower; }

I figured you would have to say if upper is true do this also what if you were asking if it is false? Then what would you do?

1 Answer

Steven Parker
Steven Parker
229,708 Points
Steven Parker
Steven Parker
229,708 Points

First, a single equal sign ("=") is an assignment operator. A comparison is a double symbol ("==").

Comparison operators create a boolean result to indicate the outcome of the comparison. So you never need to compare any boolean value to "true", because it already represents that.

if (isNaN(upper) == true || isNaN(lower) == true)  // so this test...
if (isNaN(upper) || isNaN(lower))                  // does the same thing as THIS one

And to check if a boolean value is false you can use the "not" operator ("!"):

if (!isNaN(someValue))  // this expression is true when "isNaN" is false