node.js(yargs) numbers are entering as strings?

Question

When I run solve-3 with --l=4 and --w=4, function rectangle.perimeter and rectangle.area output NaN. Why? To me it seemed like the integers entered are being converted to strings hence why I added Number(), but that did not change anything.

File 1: rect-2.js

module.exports = function(l,w,callback) {
try {
    if (l < 0 || w < 0) {
        throw new Error("Rectangle dimensions should be greater than zero: l = " + l + ", and w = " + w);
    }
    else 
        callback(null, {
            perimeter: function(l,w) {
                return (2*(l+w));
            },
            area: function(l,w) {
                return (l*w);
            }
    });
 }
catch (error) {
    callback(error,null);
}
}

File 2: solve-3.js

var argv = require('yargs')
.usage('Usage: node $0 --l=[number] --w=[number]')
.demand(['l','w'])
.argv;


var rect = require('./rect-2');

function solveRect(l,w) {
    console.log("Solving for rectangle with length: " + l + " and      width: " + w);

rect(l,w, function(err,rectangle) {
    if (err) {
        console.log(err);
    }
    else {
        console.log("The area of a rectangle with length = "+l+" and width = "+w+" is "+rectangle.area());
        console.log("The perimeter of a rectangle with length = "+l+" and width = "+w+" is "+rectangle.perimeter());
    }
  });
};

solveRect(Number(argv.l),Number(argv.w));

Answer 1

Look at the functions you've defined:

perimeter: function(l,w) {
    return (2*(l+w));
},

You expect this function to take two arguments.

Then you call it with no arguments:

rectangle.perimeter()

The arguments you're defining are shadowing the ones in the upper scope of your rect-2 file. A simple workaround is just to remove the function arguments:

perimeter: function() {
    return (2*(l+w));
},
area: function() {
    return (l*w);
}

Now these two functions are said to "close over" the l and w variables present in the upper scope.

While wrapping a string in Number() will technically work in this case, note that yargs lets you specify the types of user input values on the command line, such as the .number() syntax:

var argv = require('yargs')
    .number(['l','w'])
    .demand(['l','w'])