functions result is NaN-CodePudding

I am really new in coding therefore I am coding currently a Taximeter. Unfortunately is the result of my code when executing NaN in the console. I tried some ways to rectify my problem but those attempts did not work. I think that some variables are not in the right scope but I do not know how to fix that.

function Taximeter() {

    const y = 3.9;
    const km =  prompt("How far is your target");
    
    if (km <= 7) {
        var routePrice = 2.3;
        }   else if (km > 7) {
            let routePrice = 1.65
        var subtractedLength = km -= 7;
        var partialExpenses = subtractedLength *= routePrice ;
        var tosevenExpenses = 7 *2.3;
        var combinedExpenses = tosevenExpenses  = partialExpenses;
        }
      
        const persons = prompt("How much persons are driving with you?");
        if (persons > 8) {
            console.log("Only 8 persons can drive with you.");
        } else if (8 >= persons >= 5) {
            var personsExpenses = 5;
        } else if (0 >= persons >= 4) {
              personExpenses = 0;
        }
    
        if (km <= 7) {
            var wholeExpenses = y   km * routePrice   personsExpenses;
        } else  {
        var wholeExpenses = combinedExpenses   y   personsExpenses; 
        }
        console.log(wholeExpenses)
    };

CodePudding user response：

It would be helpful to know where exactly NaN is coming up and whether or not you are seeing NaN as the result of an Exception (if an error message was logged to the console) or if NaN is coming up as a result of your own console.log() statements. Part of the issue could be that the function prompt() returns a String, meaning that your variable km is going to be a String and not a Number. Use this line of code instead and it might fix your problem:

const km =  parseInt(prompt("How far is your target"));

EDIT:

In response to your comment, there are a couple other issues I see here. There is the issue with your first if and else if clauses where the indentation is a little off. This, as far as I can tell, should not actually affect your code, but it does make it harder to read. Here is how it should look:

if (km <= 7) {
    var routePrice = 2.3;
} else if (km > 7) {
    let routePrice = 1.65
    var subtractedLength = km -= 7;
    var partialExpenses = subtractedLength *= routePrice ;
    var tosevenExpenses = 7 *2.3;
    var combinedExpenses = tosevenExpenses  = partialExpenses;
};

Second, in those same if and else if clauses, you use the -=, *=, and = operators when they are unnecessary and may cause errors. I've never seen them used the way that you have before, so I don't know if they actually cause errors, but I would edit those clauses one more time for readability at least:

if (km <= 7) {
    var routePrice = 2.3;
} else if (km > 7) {
    let routePrice = 1.65
    var subtractedLength = km - 7;
    var partialExpenses = subtractedLength * routePrice ;
    var tosevenExpenses = 7 *2.3;
    var combinedExpenses = tosevenExpenses   partialExpenses;
};

Like with km I would also edit your persons declaration to turn that variable into a Number so that the logic operators that you use on it later work properly:

const persons = parseInt(prompt("How much persons are driving with you?"));

Another thing, like a commenter earlier pointed out, 8 >= persons >= 5 will not work the way you think it will - just edit those if and else if clauses like so to fix that error:

if (persons > 8) {
    console.log("Only 8 persons can drive with you.");
} else if(persons >= 5 && persons <= 8) {
    var personsExpenses = 5;
} else if (persons <= 4 && persons >= 0) {
    personExpenses = 0;
};

Finally, your variable declaration of personsExpenses is such that the variable will only be declared if that first else if clause resolves. You need personsExpenses to be declared no matter what, so I would declare it before and outside of any of those conditional clauses:

var personsExpenses
if (persons > 8) {
    console.log("Only 8 persons can drive with you.");
} else if(persons >= 5 && persons <= 8) {
     personsExpenses = 5;
} else if (persons <= 4 && persons >= 0) {
     personExpenses = 0;
};

That's everything that I noticed, so good luck!