Regular Expression to avoid HTML tags and empty values

Question

I have applied a textbox click validation and wanted to avoid any html tags in text box also the simple < (open tag) and >(close tag). The below code is working for but i want to add additional validations also for empty strings and other tags in html. Can some one please help modify the regex for the requirement.

function htmlValidation() 
 {
   var re = /(<([^>]+)>)/gi;

   if (document.getElementById(’<%=TextBox2.ClientID%>’).value.match(re)){ document.getElementById(’<%=TextBox2.ClientID%>’).value = “”;
          return false;
        }
   return true;
 }

Corrected Code above

I don't exactly understand what your requirements are. Do you wan't to allow specific tags, or what behaviour do you exactly want? — amon
– amon, Commented Jul 17, 2012 at 10:13
I want to exclude any html tags in the textbox...also the "<" and ">" should not be allowed — Pratik
– Pratik, Commented Jul 17, 2012 at 10:19
Why not [^<>]+ ,and check if it does NOT match this pattern. Excluding the <> will also exclude any HTML tags. — RoadBump
– RoadBump, Commented Jul 17, 2012 at 10:19
@RoadBump: Works only if we anchor your Regexp at the beginning and end of the test string. — amon
– amon, Commented Jul 17, 2012 at 10:25
Although I don't know what exactly you are coding, but in many cases it would be better to let the user correct their input instead of you deleting it. < and > can also be escaped so that they are viewed as literals, not as html operators — amon
– amon, Commented Jul 17, 2012 at 10:28

Matías Fidemraizer · Accepted Answer · 2013-07-31 07:20:25Z

3

In my opinion, I believe you'll have a good hard work if you want to validate such things.

Instead of preventing HTML content in a text box, other solution could be just html entity encode Text property, so <p>a</p> would be converted to >p<a>p<.

Result of that is you're going to render the HTML "as text" instead of getting it interpreted by Web browser.

Check this MSDN article:

http://msdn.microsoft.com/en-us/library/73z22y6h(v=vs.110).aspx

edited Jul 31, 2013 at 7:20

answered Jul 17, 2012 at 10:28

Matías Fidemraizer

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6 Comments

Pratik Over a year ago

I validating the user inputs on client side and there is requirement considering the html tags not allowed as it will hangup the other processes. So i im looking to solve at one click event only. If i get some answers will definelty post here

Matías Fidemraizer Over a year ago

@PratikGupta But if you do this way, your processes will work as expected, because you won't have HTML!

Pratik Over a year ago

there are many places where i specially don't want any special operators as this will give different meaning to the calculations handled hence i want to filter those things out on front end rather than at server side.

Matías Fidemraizer Over a year ago

@PratikGupta I believe that an HTML entity isn't an special character. Elaborate more your case if you want further details.

Pratik Over a year ago

Thank you so much for your help.I think i found the answer in my own question.I have made some mistake in the annotations of the javascript code. But now its validating all the HTML tags also inclosed in <any_tags_here>. I have also check your profile on stack it's really impressive.

|

Community · Accepted Answer · 2017-05-23 10:34:29Z

0

$("#<%= btnAdd.ClientID %>").click(function () {
            var txt = $("#<%= txtBox1.ClientID %>");
            var svc = $(txt).val();  //Its Let you know the textbox's value 
            var re = /(<([^>]+)>)/gi;
            if(txt.val()!=""){
            if (!txt.val().match(re)) {
               //my Operations 
               //goes here
                });
                return false;
            }
            else {
                alert("Invalid Content");
            }
            }
            else {
            alert("Blank value selected");
            }

I have used Jquery function to check for regular expresion. This question is a linked question with Using Jquery to add items in Listbox from Textbox

Now i can mark this as my final answer.

edited May 23, 2017 at 10:34

CommunityBot

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answered Jul 19, 2012 at 11:05

Pratik

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