Question

I’ve come across the following piece of JavaScript and would like to know what it’s doing:

function flipString(aString) {
 var last = aString.length - 1;
 var result = new Array(aString.length)
 for (var i = last; i >= 0; --i) {
  var c = aString.charAt(i)
  var r = flipTable[c]
  result[last - i] = r != undefined ? r : c
 }
 return result.join('')
}

Answer 1

It looks like some sort of encryption / obfuscation. Without knowing what filpTable looks like it’s hard to say.

function flipString(aString) {
 var last = aString.length - 1;

 // Create a new array with the length of the string
 var result = new Array(aString.length)

 // Walk through the string backwards
 for (var i = last; i >= 0; --i) {
  // Get the current character
  var c = aString.charAt(i)

  // Find the associated character in the flipTable
  var r = flipTable[c]

  // If the character wasn't in the flip table, use it as-is, else use the one we found
  // Store as (last-i) instead of (i) so it comes out backwards
  result[last - i] = r != undefined ? r : c
 }

 // Return the result as a string instead of an array
 return result.join('')
}