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   1  // Password strength meter
   2  function passwordStrength(password1, username, password2) {
   3      var shortPass = 1, badPass = 2, goodPass = 3, strongPass = 4, mismatch = 5, symbolSize = 0, natLog, score;
   4  
   5      // password 1 != password 2
   6      if ( (password1 != password2) && password2.length > 0)
   7          return mismatch
   8  
   9      //password < 4
  10      if ( password1.length < 4 )
  11          return shortPass
  12  
  13      //password1 == username
  14      if ( password1.toLowerCase() == username.toLowerCase() )
  15          return badPass;
  16  
  17      if ( password1.match(/[0-9]/) )
  18          symbolSize +=10;
  19      if ( password1.match(/[a-z]/) )
  20          symbolSize +=26;
  21      if ( password1.match(/[A-Z]/) )
  22          symbolSize +=26;
  23      if ( password1.match(/[^a-zA-Z0-9]/) )
  24          symbolSize +=31;
  25  
  26      natLog = Math.log( Math.pow(symbolSize, password1.length) );
  27      score = natLog / Math.LN2;
  28  
  29      if (score < 40 )
  30          return badPass
  31  
  32      if (score < 56 )
  33          return goodPass
  34  
  35      return strongPass;
  36  }