Storing the result of a Boolean expression isn't the strange part. Storing it in a well-named variable can make the code a lot easier to read; the name (hopefully) communicates intent, and it can separate a conditional action into separate steps.

The strange part is testing Boolean value... to return the same value as Boolean constants.

Why wasn't the Boolean result simply returned directly?

    var condn = ...;
    return condn;

The if statement isn't necessary. Even if you wanted to explicitly return only "true" or "false" - using the if statement to convert truthy and falsy results into true booleans - using double not operators removes q potentially mispredicted branch.

    var condn = ...;
    return !!condn;