JavaScript: Add two complex numbers

// Define a constructor function named Complex that represents complex numbers with real and imaginary parts.
function Complex(real, imaginary) {
  // Initialize real and imaginary parts of the complex number.
  this.real = 0;
  this.imaginary = 0;
  
  // Set the real part to the provided value or default to 0 if not provided.
  this.real = (typeof real === 'undefined') ? this.real : parseFloat(real);
  
  // Set the imaginary part to the provided value or default to 0 if not provided.
  this.imaginary = (typeof imaginary === 'undefined') ? this.imaginary : parseFloat(imaginary);
}

// Define a static method named transform for the Complex function to transform numbers to complex numbers.
Complex.transform = function(num) {
  var complex;
  
  // Check if the provided number is already a Complex instance.
  complex = (num instanceof Complex) ? num : complex;
  
  // Check if the provided number is a real number and convert it to a complex number with imaginary part 0.
  complex = (typeof num === 'number') ? new Complex(num, 0) : num;
  
  // Return the complex number.
  return complex;
};

// Define a function named display_complex to display complex numbers in a readable format.
function display_complex(re, im) {
  // If the imaginary part is 0, return only the real part.
  if(im === '0') return '' + re;
  
  // If the real part is 0, return only the imaginary part with 'i'.
  if(re === 0) return '' + im + 'i';
  
  // If the imaginary part is negative, return the real and imaginary parts combined with 'i'.
  if(im < 0) return '' + re + im + 'i';
  
  // Otherwise, return the real and imaginary parts combined with '+' and 'i'.
  return '' + re + '+' + im + 'i';
}

// Define a function named complex_num_add to add two complex numbers.
function complex_num_add(first, second) {
  // Transform the input numbers to complex numbers.
  var num1, num2;
  num1 = Complex.transform(first);
  num2 = Complex.transform(second);
  
  // Calculate the real and imaginary parts of the sum.
  var real = num1.real + num2.real;
  var imaginary = num1.imaginary + num2.imaginary;
  
  // Display the result as a complex number.
  return display_complex(real, imaginary);
}

// Create two complex numbers.
var a = new Complex(2, -7);
var b = new Complex(4,  3);

// Output the result of adding the two complex numbers.
console.log(complex_num_add(a,b));