Use document.forms[0].submit();
(0 refers to the index of the form – if you have more than one form in a page, then the first one has the index 0, second has index 1 and so on).
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How do we get JavaScript onto a web page?
You can use several different methods of placing javascript in you pages.
You can directly add a script element inside the body of page.
1. For example, to add the "last updated line" to your pages, In your page text, add the following:
<p>blah, blah, blah, blah, blah.</p>
<script type="text/javascript" >
<!-- Hiding from old browsers
document.write("Last Updated:" +
document.lastModified);
document.close();
// -->
</script>
<p>yada, yada, yada.</p>
(Note: the first comment, "<--" hides the content of the script from browsers that don't understand javascript. The "// -->" finishes the comment. The "//" tells javascript that this is a comment so javascript doesn't try to interpret the "-->". If your audience has much older browsers, you should put this comments inside your javascript. If most of your audience has newer browsers, the comments can be omitted. For brevity, in most examples here the comments are not shown. )
The above code will look like this on Javascript enabled browsers,
2. Javascript can be placed inside the <head> element
Functions and global variables typically reside inside the <head> element.
<head>
<title>Default Test Page</title>
<script language="JavaScript" type="text/javascript">
var myVar = "";
function timer(){setTimeout('restart()',10);}
document.onload=timer();
</script>
</head>
Javascript can be referenced from a separate file
Javascript may also a placed in a separate file on the server and referenced from an HTML page. (Don't use the shorthand ending "<script ... />). These are typically placed in the <head> element.
<script type="text/javascript" SRC="myStuff.js"></script>
How to read and write a file using javascript?
I/O operations like reading or writing a file is not possible with client-side javascript. However , this can be done by coding a Java applet that reads files for the script.
---What are JavaScript types?
Number, String, Boolean, Function, Object, Null, Undefined.
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How do you convert numbers between different bases in JavaScript?
Use the parseInt() function, that takes a string as the first parameter, and the base as a second parameter. So to convert hexadecimal 3F to decimal, use parseInt ("3F", 16);
How to create arrays in JavaScript?
We can declare an array like this
var scripts = new Array();
We can add elements to this array like this
scripts[0] = "PHP";
scripts[1] = "ASP";
scripts[2] = "JavaScript";
scripts[3] = "HTML";
Now our array scrips has 4 elements inside it and we can print or access them by using their index number. Note that index number starts from 0. To get the third element of the array we have to use the index number 2 . Here is the way to get the third element of an array.
document.write(scripts[2]);
We also can create an array like this
var no_array = new Array(21, 22, 23, 24, 25);
How do you target a specific frame from a hyperlink?
Include the name of the frame in the target attribute of the hyperlink. <a href=”mypage.htm” target=”myframe”>>My Page</a>
What is a fixed-width table and its advantages?
Fixed width tables are rendered by the browser based on the widths of the columns in the first row, resulting in a faster display in case of large tables. Use the CSS style table-layout:fixed to specify a fixed width table.
If the table is not specified to be of fixed width, the browser has to wait till all data is downloaded and then infer the best width for each of the columns. This process can be very slow for large tables.
Example of using Regular Expressions for syntax checking in JavaScript
...
var re = new RegExp("^(&[A-Za-z_0-9]{1,}=[A-Za-z_0-9]{1,})*$");
var text = myWidget.value;
var OK = re.test(text);
if( ! OK ) {
alert("The extra parameters need some work.\r\n Should be something like: \"&a=1&c=4\"");
}
---
How to add Buttons in JavaScript?
The most basic and ancient use of buttons are the "submit" and "clear", which appear slightly before the Pleistocene period. Notice when the "GO!" button is pressed it submits itself to itself and appends the name in the URL.
<form action="" name="buttonsGalore" method="get">
Your Name: <input type="text" name="mytext" />
<br />
<input type="submit" value="GO!" />
<input type="reset" value="Clear All" />
</form>
Another useful approach is to set the "type" to "button" and use the "onclick" event.
<script type="text/javascript">
function displayHero(button) {
alert("Your hero is \""+button.value+"\".");
}
</script>
<form action="" name="buttonsGalore" method="get">
<fieldset style="margin: 1em; text-align: center;">
<legend>Select a Hero</legend>
<input type="button" value="Agamemnon" onclick="displayHero(this)" />
<input type="button" value="Achilles" onclick="displayHero(this)" />
<input type="button" value="Hector" onclick="displayHero(this)" />
<div style="height: 1em;" />
</fieldset>
</form>
What can javascript programs do?
Generation of HTML pages on-the-fly without accessing the Web server. The user can be given control over the browser like User input validation Simple computations can be performed on the client's machine The user's browser, OS, screen size, etc. can be detected Date and Time Handling
How to set a HTML document's background color?
document.bgcolor property can be set to any appropriate color.
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How to get the contents of an input box using Javascript?
Use the "value" property.
var myValue = window.document.getElementById("MyTextBox").value;
How to determine the state of a checkbox using Javascript?
var checkedP = window.document.getElementById("myCheckBox").checked;
How to set the focus in an element using Javascript?
<script> function setFocus() { if(focusElement != null) { document.forms[0].elements["myelementname"].focus(); } } </script>
How to access an external javascript file that is stored externally and not embedded?
This can be achieved by using the following tag between head tags or between body tags.
<script src="abc.js"></script>How to access an external javascript file that is stored externally and not embedded? where abc.js is the external javscript file to be accessed.
What is the difference between an alert box and a confirmation box?
An alert box displays only one button which is the OK button whereas the Confirm box displays two buttons namely OK and cancel.
What is a prompt box?
A prompt box allows the user to enter input by providing a text box.
Can javascript code be broken in different lines?
Breaking is possible within a string statement by using a backslash \ at the end but not within any other javascript statement.
that is ,
document.write("Hello \ world");
is possible but not document.write \
("hello world");
Taking a developer’s perspective, do you think that that JavaScript is easy to learn and use?
One of the reasons JavaScript has the word "script" in it is that as a programming language, the vocabulary of the core language is compact compared to full-fledged programming languages. If you already program in Java or C, you actually have to unlearn some concepts that had been beaten into you. For example, JavaScript is a loosely typed language, which means that a variable doesn't care if it's holding a string, a number, or a reference to an object; the same variable can even change what type of data it holds while a script runs.
The other part of JavaScript implementation in browsers that makes it easier to learn is that most of the objects you script are pre-defined for the author, and they largely represent physical things you can see on a page: a text box, an image, and so on. It's easier to say, "OK, these are the things I'm working with and I'll use scripting to make them do such and such," instead of having to dream up the user interface, conceive of and code objects, and handle the interaction between objects and users. With scripting, you tend to write a _lot_ less code.
What Web sites do you feel use JavaScript most effectively (i.e., best-in-class examples)? The worst?
The best sites are the ones that use JavaScript so transparently, that I'm not aware that there is any scripting on the page. The worst sites are those that try to impress me with how much scripting is on the page.
How about 2+5+"8"?
Since 2 and 5 are integers, this is number arithmetic, since 8 is a string, it’s concatenation, so 78 is the result.
What is the difference between SessionState and ViewState?
ViewState is specific to a page in a session. Session state refers to user specific data that can be accessed across all pages in the web application.
What does the EnableViewStateMac setting in an aspx page do?
Setting EnableViewStateMac=true is a security measure that allows ASP.NET to ensure that the viewstate for a page has not been tampered with. If on Postback, the ASP.NET framework detects that there has been a change in the value of viewstate that was sent to the browser, it raises an error - Validation of viewstate MAC failed.
Use <%@ Page EnableViewStateMac="true"%> to set it to true (the default value, if this attribute is not specified is also true) in an aspx page.
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