Interview Questions and Answers

An XML document is called well-formed if it satisfies certain rules, specified by the W3C.

These rules are:

• A well-formed XML document must have a corresponding end tag for all of its start tags.
• Nesting of elements within each other in an XML document must be proper. For example, <tutorial><topic>XML</topic></tutorial> is a correct way of nesting but <tutorial><topic>XML</tutorial></topic> is not.
• In each element two attributes must not have the same value. For example, <tutorial id="001"><topic>XML</topic></tutorial> is right,but <tutorial id="001" id="w3r"><topic>XML</topic></tutorial> is incorrect.
• Markup characters must be properly specified.
• It contains only properly encoded legal Unicode characters.
• None of the special syntax characters such as < and & appear except when performing their markup-delineation roles.
• The element tags are case-sensitive; the beginning and end tags must match exactly. Tag names cannot contain any of the characters !"#$%&'()*+,/;<=>?@[\]^`{|}~, nor a space character, and cannot start with -, ., or a numeric digit.

• An XML document can contain only one root element. So, the root element of an xml document is an element which is present only once in an xml document and it does not appear as a child element within any other element.

1. A valid XML document is defined in the XML specification as a well-formed XML document which also conforms to the rules of a Document Type Definition (DTD) or a XML schema. According to JavaCommerce.com XML tutorial, "Well formed XML documents simply markup pages with descriptive tags. You don't need to describe or explain what these tags mean. In other words a well formed XML document does not need a DTD, but it must conform to the XML syntax rules. If all tags in a document are correctly formed and follow XML guidelines, then a document is considered as well formed."

2. There are languages developed specifically to express XML schemas. The document type definition (DTD) language, which is native to the XML specification, is a schema language that is of relatively limited capability, but that also has other uses in XML aside from the expression of schemas. Two more expressive XML schema languages in widespread use are W3C XML Schema (with a capital S) and RELAX NG.

wiki on XML schema     wiki on XSD or W3C XML Schema

List of XML parsing error:

HTML Interview Questions

What are the new <input> types for form validation in HTML5?

The new input types for form validation are email, URL, number, tel, and date.

Example:

JavaScript Interview Questions

11) If we want to return the character from a specific index which method is used?

The JavaScript string charAt() method 

12) What is the difference between JavaScript and JScript?

23) What is the difference between == and ===?

The == operator checks equality only whereas === checks equality, and data type, i.e., a value must be of the same type.

29) What is the output of 10+20+"30" in JavaScript?

3030

30) What is the output of "10"+20+30 in JavaScript?

102030 because after a string all the + will be treated as string concatenation operator (not binary +).

49) What is the requirement of debugging in JavaScript?

JavaScript didn't show any error message in a browser. However, these mistakes can affect the output. The best practice to find out the error is to debug the code. The code can be debugged easily by using web browsers like Google Chrome, Mozilla Firebox.

To perform debugging, we can use any of the following approaches:

• Using console.log() method
• Using debugger keyword

51) What is the role of a strict mode in JavaScript?

Strict Mode was a new feature in ECMAScript 5 that allows you to place a program, or a function, in a “strict” operating context. This strict context prevents certain actions from being taken and throws more exceptions. The statement “use strict”; instructs the browser to use the Strict mode, which is a reduced and safer feature set of JavaScript.

Benifits of using use strict: Strict mode makes several changes to normal JavaScript semantics.

• Strict mode eliminates some JavaScript silent errors by changing them to throw errors.
• Strict mode fixes mistakes that make it difficult for JavaScript engines to perform optimizations: strict mode code can sometimes be made to run faster than identical code that’s not strict mode.
• Strict mode prohibits some syntax likely to be defined in future versions of ECMAScript.
• It prevents, or throws errors, when relatively “unsafe” actions are taken (such as gaining access to the global object).
• It disables features that are confusing or poorly thought out.
• Strict mode makes it easier to write “secure” JavaScript.

How to use strict mode: Strict mode can be used in two ways, remember strict mode doesn’t work with block statements enclosed in {} braces.

• Used in global scope for the entire script.
• It can be applied to individual functions.

https://www.oracletutorial.com/plsql-tutorial/oracle-instead-of-triggers/

Summary: in this tutorial, you will learn how to use an Oracle INSTEAD OF trigger to insert data into tables via a non-updatable view.

What is an instead of trigger in Oracle

An INSTEAD OF trigger is a trigger that allows you to update data in tables via their view which cannot be modified directly through DML statements. When you issue a DML statement such as INSERT, UPDATE, or DELETE to a non-updatable view, Oracle will issue an error. Check it out for more information on the updatable view.

If the view has an INSTEAD OF trigger, it will automatically skip the DML statement and execute other DML statements instead. Note that an INSTEAD OF trigger is fired for each row of the view that gets modified. In Oracle, you can create an INSTEAD OF trigger for a view only. You cannot create an INSTEAD OF trigger for a table.

https://www.oracletutorial.com/oracle-view/oracle-updatable-view/

Summary: in this tutorial, you will learn about Oracle updatable view and how to insert or update data in the base tables through a view.