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

Daniyar Basharov
Daniyar Basharov
2,957 Points
Posted by Daniyar Basharov
Daniyar Basharov
2,957 Points

Why there is no ERROR message when I enter NaN as an argument like '100' insteat of 'hunred'

here is my code

function getRandomNumber(bottomNumber, topNumber) {
    var betweenRandomNumber = Math.floor( Math.random() * (topNumber - bottomNumber + 1)) + bottomNumber;
    if ( isNaN(bottomNumber) === true || isNaN(topNumber) === true ) {
            throw new Error("Some arguments are not a number");

    } else {
            return betweenRandomNumber;
    }
}

console.log( getRandomNumber (10, 20) );
console.log( getRandomNumber (2, '100') );
console.log( getRandomNumber (100, 500) );
console.log( getRandomNumber ('200', 300) );
console.log( getRandomNumber (1000, 10000) );

thanx

Aaron Martone
Aaron Martone
3,290 Points
Aaron Martone
Aaron Martone
3,290 Points

Because JS attempts to coerce your value to a data type depending on how you reference it. If you do '100' + 10, JS coerces the 10 number into a string and performs '100' + '10' resulting in '10010'. And '10010' is a String, despite it looking like a number to us. A String is NOT a NaN value. Try dividing 0/0, the result is NaN. So if you console.log( isNaN( 0/0 ) ); you get true. But if you log console.log(isNaN('10010')) you get false, because a String value (even though it looks numeric) is NOT a NaN value.

Mark Bacolcol
Mark Bacolcol
7,354 Points
Mark Bacolcol
Mark Bacolcol
7,354 Points

@Aaron - 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?