Euler 25

25.js

function fibonacci( n ){
  var val = '1', last = '0', tmp, i = 1
  for ( ; val.length < n; ++i ){
    tmp = val
    val = add(last, val)
    last = tmp
  }
  return i
}

function pad( str, len ){
  var pre = '', i = 0, max = len - str.length
  for ( ; i < max; ++i ) pre += '0'
  return pre + str
}

function add( s1, s2 ){
  var i = s2.length - 1, out = '', rem = val = 0
  s1 = pad(s1, s2.length)
  for ( ; i >= 0; i-- ) {
    val = parseInt(s1[i], 10) + parseInt(s2[i], 10) + rem
    rem = val > 9 ? (val = val % 10, 1) : 0
    out = val + out
  }
  return ( rem || '' ) + out
}

console.log( fibonacci(1000) )

25.py

def fibonacci( n ):
  val = '1'
  last = '0'
  tmp = ''
  i = 1
  while ( len(val) < n ):
    tmp = val
    val = add(last, val)
    last = tmp
    i = i + 1
  return i

def pad( str, length ):
  padding = ''
  i = 0
  max = length - len(str)
  while ( i < max ):
    padding = padding + '0'
    i += 1
  return padding + str

def add( str1, str2 ):
  i = len(str2) - 1
  remainder = 0
  result = ''
  num1 = ''
  num2 = ''
  val = 0
  str1 = pad(str1, len(str2))
  while ( i >= 0 ):
    num1 = int( str1[i] )
    num2 = int( str2[i] )
    val = num1 + num2 + remainder
    if ( val > 9 ): 
      val = val % 10
      remainder = 1
    else:
      remainder = 0
    result = str(val) + result
    i = i - 1
  if ( remainder != 0 ):
    result = str(remainder) + result
  return result

print( fibonacci(1000) )