Returning a string from a parallel array

Question

I am sorry for the very newbie question, but this is driving me mad.

I have a word. For each letter of the word, the characters position in one array is found and then returns the character at the same position found in a parallel array (basic cipher). This is what I already have:

*array 1 is the array to search through*
*array 2 is the array to match the index positions*

var character
var position
var newWord 

for(var position=0; position < array1.length; position = position +1) 
{
    character = array1.charAt(count);     *finds each characters positions*
    position= array1.indexOf(character);  *index position of each character from the 1st array*
    newWord = array2[position];           *returns matching characters from 2nd array*
}

document.write(othertext + newWord);      *returns new string*

The problem I have is that at the moment the function only writes out the last letter of the new word. I do want to add more text to the document.write, but if I place within the for loop it will write out the new word but also the other text inbetween each word. What i actually want to do is return the othertext + newWord rather than document.write so that I can use it later on. (just using doc.write to text my code) :-)

I know its something really simple, but I cant see where I am going wrong. Any advice? Thanks Issy

Answer 1

A good way of structuring your code and your question is that you define a function that you need to implement. In your case this could look like:

function transcode(sourceAlphabet, destinationAlphabet, s) {
  var newWord = "";

  // TODO: write some code

  return newWord;
}

That way, you clearly state what you want and which parameters are involved. It is also easy to write automatic tests later, for example:

function testTranscode(sourceAlphabet, destinationAlphabet, s, expected) {
  var actual = transcode(sourceAlphabet, destinationAlphabet, s);
  if (actual !== expected) {
    document.writeln('<p class="error">FAIL: expected "' + expected + '", got "' + actual + '".</p>');
  } else {
    document.writeln('<p class="ok">OK: "' + actual + '".');
  }
}

function test() {
  testTranscode('abcdefgh', 'defghabc', 'ace', 'dfh');
}

test();