Check for a specific character string using javascript

Question

How can I write ad check for a specific character string in a text field?

If someone types in this identification number in a textfield.
Upon submit, it will look if it starts with "D" IE: D959344843

If it does, display a DIV on the page. If not, prompt an error alert message.

-=-=-=-=-=-=-=-=-=-=-=--=
New addition
How can I code this on my page and make it work?

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Test</title>

<script type="text/javascript">
var mystring = 'D59344843';

if(mystring.substring(0, 1) == 'D'){
//display a DIV
alert('cool');
}else{
alert('error is no kewl');
}
</script>

</head>

<body>
<input name="yourtextfield" value="" type="text" />
<input name="" type="submit" />
</body>
</html>

please take a look at the jsfiddle i put up i attached an onclick to the submit button and formatted the logic into a function but u can modified it. — KJYe.Name
– KJYe.Name, Commented Feb 14, 2011 at 18:22

Chris Sobolewski · Accepted Answer · 2011-02-14 17:53:09Z

string = 'D959344843'; x = string.match(/^D/i); if(x){ //function to show div }

This is using regex. If the character ([d]) is at the beginning of the string (^), this will match and return true. The /i makes the query non-case sensitive.

Another way to do this would be

string = 'D959344843'; if(string.charAt(0) == 'D' || 'd'){ //function to show div }

This will look for the character at position 0 in the string (the first character). If it is a D or a d, it will do whatever is in the if block.

KJYe.Name · Accepted Answer · 2011-02-14 18:56:09Z

var mystring = 'D59344843'; //or for your textfield w/ id document.getElementById('yourtextfield').value; if(mystring.substring(0, 1) == 'D'){ //display a DIV alert('cool'); }else{ alert('error is no kewl'); }

Update:

Here is the jsfiddle

html:

<input name="yourtextfield" id="yourtextfield" value="" type="text" /> <a href="#" onClick="checkMahStr()">Test</a> <div id="class1" style="display: none">afasdfdsafsdafdsafsdfsdaf</div>

JavaScript:

function checkMahStr() { var mystring = document.getElementById('yourtextfield').value; if (mystring.substring(0, 1) == 'D') { document.getElementById('class1').style.display = 'block'; } else { document.getElementById('class1').style.display = 'none'; alert('error is no kewl'); } }

kjy112, I've been trying to implement this on my page with no luck. Could you please look at my latest edit addition at the top and help me out please?
How this is really nice! How would you make the "display DIV" part inside the HTML page? Only thing missing at the moment and can't make it work.
Just a simple div with text and image. Here's an example: <a href="#" onClick="showLinks('class1');return false;">Test</a> <div id="class1" style="display: none">afasdfdsafsdafdsafsdfsdaf</div>
Thanks kjy112, this worked out perfectly! I need to buy you a beer now... And yep, that's my little dog lol. Was wondering about an additional verification possibility. How can we format this so it checks for the starting letter "D" and also check and make sure there are 9 numbers following it?

Gabriel S. · Accepted Answer · 2011-02-14 17:52:29Z

Checking if a string contains a substring can be achieved by using regular expressions. Here's an example:

var r = /^D/; r.test('Hello World !'); // Returns false r.test('D9756612'); // Returns true;

More information about regular expressions can be found here

If that doesn't help you, please describe your problem more precisely !

EDIT: Mis-read your example and corrected accordingly. If you just want to check the first character of a string, go for ferrari fan's answer, using indexOf(). If you want to be able to do multiple checks at the same time, I recommend you use regular expressions rather than multiple conditional structures.

Jaime Garcia · Accepted Answer · 2011-02-14 17:59:42Z

0

You could just use the indexOf() function

if (myString.indexOf('D') == 0) { ... perform your logic here since 'D' was found .... } else { ... your alert goes here ... }

edited Feb 14, 2011 at 17:59

answered Feb 14, 2011 at 17:51

Jaime Garcia

7,1748 gold badges53 silver badges61 bronze badges

2 Comments

Gabriel S. Over a year ago

This checks if the whole string contains a 'D', not just the first character of the string. One would rather use myString.indexOf('D') === 0

Chris Sobolewski Over a year ago

This will return if D is in the string at all. The user seemed to be asking if the string STARTED with D.

Collectives™ on Stack Overflow

Check for a specific character string using javascript

4 Answers 4

Comments

10 Comments

Comments

2 Comments

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

10 Comments

Comments

2 Comments

Related