To validate textbox in javascript

Dear all,

Validating through server side is required to check like the same name that the user entered is already there in database or not. Simple validations like user entered correct text or is the user had entered some special characters which will crash application. We can restrict entering special characters. On key press we can restrict entering the values by the user, but how can we restrict the user on paste of the special characters in a text box. Of course we can restrict paste of drag and drop on a text box.

Let us see how can do this using asp.net application with JavaScript

To restrict some special character we need to add escape sequence

Check the some of the special characters which requires escape sequence

//for slash it requires \\\\  etc.,

var r = new RegExp("[.,_0-9a-zA-Z'&\r \\\\]", "g"); 

//2 argument that we need to pass is Client id of the text box which you want to check and the maximum length of the text that you want to allow in a text box

function RestrictDescription(txtName, maxLength)
    {
//This will capture the keycode when the user pressed any key in application   
        var exp = String.fromCharCode(window.event.keyCode) 
        var address=document.getElementById(txtName);
//Below line will have the special characters that is not allowed you can add if you want more for some characters you need to add escape sequence
        var r = new RegExp("[-_,/'().0-9a-zA-Z \r]", "g");
        if (exp.match(r) == null)
        {
            window.event.keyCode = 0
            return false;
        }        
        if(address.value.length >= maxLength)
        {   
            alert("Maximum of 255 characters are allowed to be entered as a description"); 
		//Truncated to 255 character and stored in the textbox
            address.value = address.value.substring(0, maxLength);    
            return false;
        }
    }  




From server side(Code behind we need can call the function like the below code



txtsubmit.Attributes.Add("onkeypress", "javascript:return RestrictDescription('" + txtsubmit.ClientID + "',255)");

//To restrict on drop of any special charcater and on paste of any special character we can use the below code from server side

txtsubmit.Attributes.Add("ondrop", "javascript:return false");

txtsubmit.Attributes.Add("onpaste", "javascript:return false");