Get URL Parameters (QueryStrings) using Javascript
Nearly all server-side programming languages have built-in functions to retrieve querystring values of a URL. In web browsers you can access the querystring with client-side JavaScript, but there is no standard way to parse out the name/value pairs. So here is a function to return a parameter you specify. The following javascript code snippet facilitates Javascript's built in regular expressions to retrieve value of the key. Optionally, you can specify a default value to return when key does not exist.
function getQuerystring(key, default_)
{
if (default_==null) default_="";
key = key.replace(/[\[]/,"\\\[").replace(/[\]]/,"\\\]");
var regex = new RegExp("[\\?&]"+key+"=([^&#]*)");
var qs = regex.exec(window.location.href);
if(qs == null)
return default_;
else
return qs[1];
}
The getQuerystring function is simple to use. Let's say you have the following URL:
http://www.bloggingdeveloper.com?author=bloggingdeveloper
and you want to get the "author" querystring's value:
var author_value = getQuerystring('author');
If you execute code shown in the above line, the author_value will be bloggingdeveloper. The query string is parsed by the regular expression and the value of the author_value parameter is retrieved. The function is smart in a couple of ways. For example, if you have an anchor in your URL like our example URL above does (#top) the getQuerystring() function knows to stop before the # character. Also, if a requested parameter doesn't exist in the query string and the default value is not specified as a function parameter then an empty string is returned instead of a null.
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The javascript code below shows how to set the focus on an Input Field / Form Field / Html Element (Textbox) when the page is loaded.
<html>
<head>
<script type="text/javascript">
function setFocus()
{
document.getElementById("name").focus();
}
</script>
</head>
<body onload="setFocus()">
<form>
Name: <input type="text" id="name" size="30"><br />
Surname: <input type="text" id="surname" size="30">
</form>
</body>
</html>
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In ASP.NET 1.x, it is not possible to programmatically set focus to a web server control without using the JavaScript's focus() function after submit (on Page Load / after Postback). You may find the details on how to set focus to web controls in ASP.NET 1.x in one of my previous articles: Set Focus After PostBack in ASP.NET 1.x - Setting Focus to an ASP.NET Control
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Management of control focus is one of the common tasks when building web applications with effective and friendly user interface. In order to set focus on a certain control such as textboxes, buttons dropdowns after postback / after submit / on Page Load in ASP.NET 1.x, we can use a dynamic javascript block that facilitates Javascript’s focus() function.
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The JavaScript parseFloat() function, parses a string and returns the first floating point number in the string.
The parseFloat() function determines if the first character in the string argument is a number, parses the string from left to right until it reaches the end of the number, discards any characters that occur after the end of the number, and finally returns the number as a number (not as a string).
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The JavaScript parseInt() function parses a string and returns the first integer in a string.
There are two arguments one of which is mandatory string argument that is the string which is parsed to return the integer. The other argument is the optional radix argument that specifies the base of the integer and can range from 2 to 36. For example, 16 is the hexidecimal base (0123456789ABCDEF).
If no radix argument is provided or if it is assigned a value of 0, the function tries to determine the base:
- If the string begins with "0x", the radix is 16 (hexadecimal)
- If the string begins with "0", the radix is 8 (octal). This feature is deprecated
- If the string begins with any other value, the radix is 10 (decimal)
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Displaying the last modified date of a web page using Javascript is just a matter of diplaying the document.lastModified property of Javascript.
document.lastModified;
In order for this property to work, the server has to send the information to the browser. which is widely supported by the browsers nowadays.
When a server does not send a lastModified date information to the browser, Netscape and Opera give a last modification date of 01/01/1970 at 00:00:00 hrs, while Internet Explorer gives today. So it is always a good practice to test the server if it is sending the necessary information to the browser before using this script.
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Remote desktop connections remain active until the logged in user selects "Log Off" from the Start Menu. If a user closes the remote desktop window without logging off, the user will still remain logged on.
Only up to two simultaneous Remote Desktop connections are allowed by default and active and disconnected sessions are calculated in this connection limit.
If a third simultaneous attempt is made to login to the server "The terminal server has exceeded the maximum number of allowed connections" error will be shown to the user, and they will be unable to complete the login process.
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JavaScript is different from other programming languages by containin both undefined and null values, which may cause confusion.
null is a special value meaning "no value". null is a special object because typeof null returns 'object'.
On the other hand, undefined means that the variable has not been declared, or has not been given a value.
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Doing many string concatenation operations can be a major hit on performance even in Javascipt.
Using + to concatenate string pieces into a huge string is not the correct and the only way. Since string concatenation results in too many intermediate strings and concatenation operations, it performs poorly.
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