IMAGINARY Function

IMAGINARY.js

// Copyright (c) 2012 Sutoiku, Inc. (MIT License)

function IMAGINARY(inumber) {
  // Return 0 if inumber is equal to 0
  if (inumber === 0 || inumber === '0') return 0;

  // Handle special cases
  if (['i', 'j'].indexOf(inumber) >= 0) return 1;
  
  // Normalize imaginary coefficient
  inumber = inumber.replace('+i', '+1i').replace('-i', '-1i').replace('+j', '+1j').replace('-j', '-1j');
  
  // Lookup sign
  var plus = inumber.indexOf('+');
  var minus = inumber.indexOf('-');
  if (plus === 0) plus = inumber.indexOf('+', 1);
  if (minus === 0) minus = inumber.indexOf('-', 1);
  
  // Lookup imaginary unit
  var last = inumber.substring(inumber.length - 1, inumber.length);
  var unit = (last === 'i' || last === 'j')
  
  if (plus >= 0 || minus >= 0) {
    // Return error if imaginary unit is neither i nor j
    if (!unit) return '#NUM!';

    // Return imaginary coefficient of complex number
    if (plus >= 0) {
      return (isNaN(inumber.substring(0, plus)) || isNaN(inumber.substring(plus + 1, inumber.length - 1))) ?
        '#NUM!' :
        Number(inumber.substring(plus + 1, inumber.length - 1));
    } else {
      return (isNaN(inumber.substring(0, minus)) || isNaN(inumber.substring(minus + 1, inumber.length - 1))) ?
        '#NUM!' :
        -Number(inumber.substring(minus + 1, inumber.length - 1));
    }
  } else {
    if (unit) {
      return (isNaN(inumber.substring(0, inumber.length - 1))) ? '#NUM!' : inumber.substring(0, inumber.length - 1);
    } else {
      return (isNaN(inumber)) ? '#NUM!' : 0;
    }
  }
}