PASSWORD STRENGTH METER (jquery)
/**
* Evaluate the strength of a user's password.
*
* Returns the estimated strength and the relevant output message.
*/
Drupal.evaluatePasswordStrength = function(value) {
  var strength = "", msg = "", translate = Drupal.settings.password;
  var hasLetters = value.match(/[a-zA-Z]+/);
  var hasNumbers = value.match(/[0-9]+/);
  var hasPunctuation = value.match(/[^a-zA-Z0-9]+/);
  var hasCasing = value.match(/[a-z]+.*[A-Z]+|[A-Z]+.*[a-z]+/);
  // Check if the password is blank.
  if (!value.length) {
    strength = "";
    msg = "";
  }
  // Check if length is less than 6 characters.
  else if (value.length < 6) {
    strength = "low";
    msg = translate.tooShort;
  }
  // Check if password is the same as the username (convert both to lowercase).
  else if (value.toLowerCase() == translate.username.toLowerCase()) {
    strength  = "low";
    msg = translate.sameAsUsername;
  }
  // Check if it contains letters, numbers, punctuation, and upper/lower case.
  else if (hasLetters && hasNumbers && hasPunctuation && hasCasing) {
    strength = "high";
  }
  // Password is not secure enough so construct the medium-strength message.
  else {
    // Extremely bad passwords still count as low.
    var count = (hasLetters ? 1 : 0) + (hasNumbers ? 1 : 0) + (hasPunctuation ? 1 : 0) + (hasCasing ? 1 : 0);
    strength = count > 1 ? "medium" : "low";
    msg = [];
    if (!hasLetters || !hasCasing) {
      msg.push(translate.addLetters);
    }
    if (!hasNumbers) {
      msg.push(translate.addNumbers);
    }
    if (!hasPunctuation) {
      msg.push(translate.addPunctuation);
    }
    msg = translate.needsMoreVariation +"<ul><li>"+ msg.join("</li><li>") +"</li></ul>";
  }
  return { strength: strength, message: msg };
};

Password Strength Meter

regex, javascript, jquery

jQuery