NodeJS II

Callbacks

• First parameter is always an error

Code using Callbacks

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

Execute the function using Callbacks

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

function solveRect(l,b) {
    console.log("Solving for rectangle with l = "
                + l + " and b = " + b);
    rect(l,b, function(err,rectangle) {
        if (err) {
   console.log(err);
}
else {
   console.log("The area of a rectangle of dimensions length = "
                 + l + " and breadth = " + b + " is " + rectangle.area());
            console.log("The perimeter of a rectangle of dimensions length = "
                 + l + " and breadth = " + b + " is " + rectangle.perimeter());
}
    });
};

solveRect(2,4);
solveRect(3,5);
solveRect(-3,5);

Installing package (yargs)

var argv = require('yargs')

    .usage('Usage: node $0 --l=[num] --b=[num]')

    .demand(['l','b'])

    .argv;

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

function solveRect(l,b) {

    console.log("Solving for rectangle with l = "

                + l + " and b = " + b);

    rect(l,b, function(err,rectangle) {

if (err) {

   console.log(err);

}

else {

            console.log("The area of a rectangle of dimensions length = "

                  + l + " and breadth = " + b + " is " + rectangle.area());

   console.log("The perimeter of a rectangle of dimensions length = "

                  + l + " and breadth = " + b + " is " + rectangle.perimeter());

}

    });

};

solveRect(argv.l,argv.b);

Execute using Yargs

node solve-3 -l=2 -b=2