Römisch Dezimal

Dieses Javascript zum umwandeln verschiedener Zahlensysteme stammt auch von unserem User „Vollautomatisch“.

Mit dem Javascript könnt ihr Zahlen vom gewohnten und allgemein gebräuchlichen Dezimalsystem in römische Zahlen umwandeln.

Das ganze funktioniert natürlich auch umgekehrt, d. h. ihr könnt mit dem Javascript auch römische Zahlen in Dezimalzahlen umwandeln 🙂

<!-- präsentiert von kostenlose-javascripts.de --> <script type='text/javascript'> <!-- /******************************************************************** * This function converts numbers from the decimal system * * correctly to the Roman system. The Roman letters are: * * I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000 * * That means: DXX = 520, MMMMCLVI = 4156 * * If a letter with a lower value stays in front of a higher * * one, the value of the lower one will be substracted from * * the other. * * That means: IV = 4 (5 - 1 = 4), MCM = 1900 (1000 + (1000 - 100)) * ********************************************************************/ function dec2rom (dec) { var dec = '' + dec; // Converts the decimal "dec" to a string while (dec.substr(0, 1) == '0') { dec = dec.substring(1, length); } // Remove zeroes in front to avoid converting to the octal system var num = parseInt(dec); // Converting string to decimal var thousand = 0; // Counts, how often we substracted 1000 from the decimal while (num > 1000) { num -= 1000; thousand++; } // Required to lower the number dec = num + ''; // Overwrites "dec" with the new - under circumstances lower - number var rN = ''; // Prepare empty string (the result) var length = dec.length; // Length of the string var adds = new Array('I', 'X', 'C', 'M'); // These are letters which can be placed next to eacht other (8 = "VIII"), sorted asc. var noAdds = new Array('V', 'L', 'D'); // These letters cannot be put next to each other ("VV" does not exist), sorted asc. for (var i = 0; i < length; i++) // This loop will extract each digit from the decimal and handle its "translation" { var d = dec.substr(i, 1); // Actual digit of "dec" var pos = length - 1 - i; // Reverse position in arrays if (d == 0) { continue; } // The Romans did not know the zero else if ( (d == 1) || (d == 2) || (d == 3) ) // Letters, that are added (like "III") { for (var j = 0; j < d; j++) { rN += adds[pos]; } // A loop that addes 1, 2 or 3 times the given letter (like "III", "XXX") } else if (d == 4) { rN += adds[pos] + noAdds[pos]; } // Adds two letters, if the digit is "4"; in case of 4: "IV" else if (d == 5) { rN += noAdds[pos]; } // Simply add the non-addable signs ("V", "L", "D") else if ( (d == 6) || (d == 7) || (d == 8) ) // Comparable to case "1", "2" or "3" { rN += noAdds[pos]; // Sign, that is used in case "5" for (var k = 5; k < d; k++) { rN += adds[pos]; } // 1, 2 or 3 the given letter (like "III", "XXX") } else if (d == 9) { rN += adds[pos] + adds[pos + 1]; } // Comparable to "4", but only with addable letters } for (var m = 0; m < thousand; m++) { rN = 'M' + rN; } // At beginning, we substracted "thousand" times 1000; now, we add them document.deciromanform.rom.value = rN.toUpperCase(); // Writes the Roman string in capital letters in the Roman text input } /************************************************* * This function converts numbers from the * * Roman system correctly to the decimal system. * *************************************************/ function rom2dec (rom) { var rom = ('' + rom).toUpperCase(); // Make sure that "rom" is a string var dec = 0; // Starting value of the decimal number var length = rom.length; // Declarates string length var letters = 'IVXLCDM'; // All the signs used in Roman codes var values = new Array(1, 5, 10, 50, 100, 500, 1000); for (var i = 0; i < length; i++) // Substracts letters from the Roman code { var l = rom.substr(i, 1); // "l" = letter on "i"-position var posl = letters.indexOf(l); // Position of "l" in "letters" if (i != (length - 1)) // Condition to avoid wrong indexes { var lA = rom.substr((i+1), 1); // "lA" = letter after "l" var poslA = letters.indexOf(lA); // Position of "lA" in "letters" } else { poslA = 0; } // Alternative value for the last run of the loop if (posl >= poslA) { dec += values[posl] } // Adds value to variable "dec" else if (posl < poslA) { dec = dec - values[posl] + values[poslA]; i++; } // The special feature of Roman numbers (read info box to function "dec2roman") } document.deciromanform.dec.value = dec; // Writes the decimal in the Roman text input } //--> </script> <form name="deciromanform"> <table> <tr> <th class="measureTh">Decimal number</th> <td> </td> </tr> <tr> <td><input type="text" name="dec" id="dec" /></td> <td><input type="button" id="decButton" onclick="dec2rom(document.getElementById('dec').value)" value="umwandeln" /></td> </tr> <tr> <th class="measureTh">Roman number</th> <td> </td> </tr> <tr> <td><input type="text" name="rom" id="rom" /></td> <td><input type="button" id="romButton" onclick="rom2dec(document.getElementById('rom').value)" value="umwandeln" /></td> </tr> </table> </form> <br /> JavaScript von <a href="http://www.kostenlose-javascripts.de/javascripts/mathematik/roemisch-dezimal/" target="_blank">kostenlose-javascripts.de</a> <br /> <!-- präsentiert von kostenlose-javascripts.de -->