Javascript，检查相同字符

Question

I got to make a script for checking an input box (password) for the same characters occuring twice. This should be used alongside with regex validation (that's already fully working).
To succeed I know that I need to use a (for?) loop somehow, that checks if one character appear twice. Now this is a kind of odd thing to ask for. I know. But I'm not entirely sure about the conditions for the function. If anyone have any suggestions around how this could be made, that would be great. An example: "ABad12" - will pass, whilst "AbAc12" will return false. Thanks in advance.

function checkForm(form)


{

 var re = /^\w{6,10}$/;

  if(!re.test(form.pwd1.value)) {
  alert("Error: Password has to be in-between 6-10 characters!");
  form.inputfield.focus();
  return false;
  }


}

Above goes an example of what script I'd like to combine it with (among with more regex validations).

Answer 1

That's how I would do this:

var str = "ABad12",
    valid = str.split("").filter(function(e, i, a) {
        return a.indexOf(e) !== i;
    }).length === 0;

if (!valid) {
    // ...
}

But note that array filter() method is not available in old browsers, so check browser compatibility page in advance.

Answer 2

you do not need a for loop. a simple regex is enough:

(\w)\1+


var validateRegEx=/(\w)\1+/;
validateRegEx.test("aa") -> return true;
validateRegEx.test("ab") -> return false;

Answer 3

Here's simple (though a bit brute-force) code, pure JavaScript with no regexp:

function check(s) {
  var i;
  for(i = 0; i < s.length - 1; i++) {
    if(s.indexOf(s.substring(i,i+1), i+1) >= 0) {
      return false;
    }
  }
  return true;
}

It simply processes the string from the start and checks for each character whether that character appears later in the string.

If you integrate this into your code, you could issue a specific message. Before return false , you could call an error reporting function asking it to show eg 'Error: character “' + s.charAt(i) + '” appears more than once.'