Why does this regular expression work outside of the javascript function, but not inside?

Question

Why does this regular expression work outside of the javascript function, but not inside?

Ok, so I'm new to regex, not to mention Javascript.

I am trying to work on a form validation project, and I found a site on which they have a list of useful examples of regular expressions for various things here , which has a few for email authentication, which I am trying now.

In any case, following this example to validate the form in w3schools, I was able to get it to work correctly using their example, and the regular expression works outside the javascript function, but for some reason, when I call it inside the function, it returns undefined ,

Here is my code:

<html>
  <head>
    <title>formzz validate-jons</title>
      <script type="text/javascript">
        pattern = new RegExp("^[0-9a-zA-Z]+@[0-9a-zA-z]+[\.]{1}[0-9a-zA-Z]+[\.]?[0-9a-zA-Z]+$");

        function valid8email(field, txt)
        {
          with(field)
          {
            //at_pos = value.indexOf('@');
            //dot_pos = value.lastIndexOf('.');

            if(!pattern.test(value)) //at_pos < 1 || (dot_pos - at_pos) < 2)
            {
              alert(txt);
              return false;
            }
            else
            {
              return true;
            }
          }
        }

        function valid8(form)
        {
          with(form)
          {
            if(valid8email(email, "you must enter an email address") == false)
            {
              email.focus();
              return false;
            }
          }
        }
      </script>
    </head>
    <body>
      <form action="#" method="POST" onsubmit="return valid8(this)">

        Email: <input type="text" name="email" size="30" />
        <input type="submit" value="clicky-click" />

    </form>

    <script type="text/javascript">
      alert(pattern.test(""));
    </script>
  </body>
</html>

... script .

javascript :

"" -
'undefined' javascript
regex , true, script

? .

+3

javascript regex email validation undefined

邪悪歌 01 . '10 0:09

1

Nick Craver · Answer 1 · 2010-12-01T00:18:13+0000

, pattern field.pattern ( HTML5), with(), , . - pattern1, .

with , :)

with :

var pattern = new RegExp("^[0-9a-zA-Z]+@[0-9a-zA-z]+[\.]{1}[0-9a-zA-Z]+[\.]?[0-9a-zA-Z]+$");

function valid8email(field, txt) {
    if (!pattern.test(field.value))
    {
        alert(txt);
        return false;
    }
    else {
        return true;
    }
}

function valid8(form) {
    if (valid8email(form.email, "you must enter an email address") == false) {
        form.email.focus();
        return false;
    }
}

.

Why does this regular expression work outside of the javascript function, but not inside?

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