'use strict';

const sum = (a, b, callback) => {

if (typeof a === 'number' && typeof b === 'number') {

callback(null, a + b);

} else {

callback(new Error('a and b should be numbers'));

}

};

const x = 2;

const y = 3;

sum(x, y, (err, total) => {

if (err) {

console.error({ x, y, err });

return;

}

console.log({ x, y, total });

});

const z = 7;

const c = 'A';

sum(z, c, (err, res) => {

if (err) {

console.error({ z, c, err });

return;

}

console.log({ z, c, res });

});