Solved

first character in a string

Posted on 2006-06-12
4
1,098 Views
Last Modified: 2012-08-14
hi,
how do i find in javascript whether the first character in a string is a number,alphabet,or a special character?
0
Comment
Question by:jiniasp
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
4 Comments
 
LVL 49

Accepted Solution

by:
Roonaan earned 50 total points
ID: 16884930
if(mystring.match(/^[a-z]/i)) {
  //alpha
} else if(mystring.match(/^\d/i)) {
  //numeric
} else {
  //other
}

-r-
0
 

Author Comment

by:jiniasp
ID: 16885188
Thanks Roonaan ur code worked.
If u don't mind, could u please explain the code above.
Can isNaN(x) function be used to find whether first character is number or not?
0
 
LVL 49

Expert Comment

by:Roonaan
ID: 16885209
You can use isNaN(mystring.substring(0,1))

As to the above code. It uses regular expression:
/^[a-z]/i can be explained as:

^ - start of string
[a-z] - a single a-z character
/i - case insensitive search

\d is shorthand for [0-9], resulting in searching for a number at the start of a string: ^\d

-r-
0
 
LVL 3

Expert Comment

by:MrHorizontal
ID: 16885405
Put these special prototype functions anywhere in your javascript:

      String.prototype.IsAlpha= function()
      {
            return (this.match(/[A-Za-z]/g) ? true : false);
      }

      String.prototype.IsNumeric= function()
      {
            return (this.match(/[0-9]/g) ? true : false);
      }

      String.prototype.IsSpecial= function()
      {
            return (this.match(/[^A-Za-z0-9]/g) ? true : false);
      }

These mean that when you have a string or a number variable, you can simply call stringvar.IsAlpha() stringvar.IsSpecial() or stringvar.IsNumeric() which return true or false accordingly.

with your string, since you want the first character only do the following:

      var mystring = '0123AbCdEfG£$%^&';

      var isNumeric = (mystring+'').charAt(0).IsNumeric(); // check for number
      var isAlpha = (mystring+'').charAt(0).IsAlpha(); // check for alpha
      var isSpecial = (mystring+'').charAt(0).IsSpecial(); // check for alpha
      var isAlphaNumeric = (mystring+'').charAt(0).IsAlpha() || (mystring+'').charAt(0).IsNumeric(); // check for alpha

the only ones that will be true will be isNumeric and isAlphaNumeric, the others should be false.

you can also derive isSpecial by doing

      var isSpecial = !(mystring+'').charAt(0).IsAlpha() && !(mystring+'').charAt(0).IsNumeric();

Similarly, like Roonaan's layout, you can use the statements in an if or switch statement:

      if ((mystring+'').charAt(0).IsNumeric())
      {
            // numeric
      }
      else if ((mystring+'').charAt(0).IsAlpha())
      {
            // alpha
      }

Because these are prototypes of the base String object, this means you can use these as methods for *any* string, whether they are a variable, in an array or wherever.

In case you're wondering, I'm forcing (mystring+'') in the example above to force the variable into a string and test it, without changing the basic variable. If you try doing it with a number and you call the method, you'll get an exception.
0

Featured Post

Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Tools for analysis of code 4 51
ModalPopup  question 22 39
Link Anchor Not working 9 51
replacing inline javascript with jquery 4 46
Nothing in an HTTP request can be trusted, including HTTP headers and form data.  A form token is a tool that can be used to guard against request forgeries (CSRF).  This article shows an improved approach to form tokens, making it more difficult to…
This article demonstrates how to create a simple responsive confirmation dialog with Ok and Cancel buttons using HTML, CSS, jQuery and Promises
The viewer will learn the basics of jQuery, including how to invoke it on a web page. Reference your jQuery libraries: (CODE) Include your new external js/jQuery file: (CODE) Write your first lines of code to setup your site for jQuery.: (CODE)
The viewer will learn the basics of jQuery including how to code hide show and toggles. Reference your jQuery libraries: (CODE) Include your new external js/jQuery file: (CODE) Write your first lines of code to setup your site for jQuery…

696 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question