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JavaScript The Solution

Posted by mebula
mebula
4,931 Points

Question about booleans in conditional statements

When testing booleans in a conditional statement, do you not have to include whether you want to test for it being true vs false? Below is some code I wrote for one of the JavaScript Workshops. However, when I checked it against the official solution, they had the conditional written as: (isNan(num1) || isNaN(num2))

I'm confused as to why you do not need to declare whether you're testing it to be true or false.

if (num2 == 0) {
    alert("The second number is 0. You can't divide by zero. Reload and try again.");
} else if { (isNaN(num1) === true || isNaN(num2) === true) {
    alert("At least one of your inputs is not a number. Please try again!");
} else {
    message = "<h1>Math with the numbers " + num1 + " and " + num2 + "</h1>";
    document.write(message);
}

3 Answers

Jean-Paul REMAN
Jean-Paul REMAN
6,004 Points
Jean-Paul REMAN
Jean-Paul REMAN
6,004 Points

An exemple : var hello = "Hi";

you could write : if (hello) { .... ; } // a variable hello exists then hello is true. if ( hello === true ) is the same of if ( hello ) if ( sun ) {..... ;} else {........ ; } // There is no variable named sun , then sun is false. if ( sun === true ) is the same of if ( sun )

Jon Wood
Jon Wood
9,884 Points
Jon Wood
Jon Wood
9,884 Points

The isNan function evaluates to return a true or false. So if the isNan(num1) evaluates to true, the if statement will interpret it like if(true).

Peter Retvari
seal-mask
.a{fill-rule:evenodd;}techdegree
Peter Retvari
Full Stack JavaScript Techdegree Student 8,392 Points
Peter Retvari
.a{fill-rule:evenodd;}techdegree
Peter Retvari
Full Stack JavaScript Techdegree Student 8,392 Points

Dears,

Could you please help me? I also solved the solution and wanted to ask the same question, however I found this topic. But I still don't understand why "(isNan(num1) || isNaN(num2))" is equivalent with (isNan(num1)=true || isNaN(num2)=true). I wonder if you could explain it. Thanks