HTML DOM Interview Questions and Answers

13 Aug

DOM(Document Object Model) is a programming API for HTML and XML doc. The Document object has various properties that refer to other objects which allow access to and modification of document content.

What is the main function of DOM?

The DOM is known as Document object model and it allows the accessing of the documents like HTML and XML.
It allows a platform to be language neutral and provide an interface that allows the dynamic usage of the scripts and programs to access the content.
It also provides a way to update the content, structure and style of the document and a way to represent it in any language.
It is used with the language and used to create the objects that can be used as a model to allow the interface to be developed with ease.

What are the HTML DOM Properties?

These are some typical DOM properties:

innerHTML – the inner text value of x (a HTML element)
nodeName – the name of x
nodeValue – the value of x
parentNode – the parent node of x
childNodes – the child nodes of x
attributes – the attributes nodes of x

What are the levels involved in DOM?

DOM is used to define the object with its properties that is having all the document elements and the methods allowing access to them.
DOM is known as document object model is divided into three different parts or levels:
Core DOM is used for the standard model for all the structures and the structured documents.
XML DOM is used as a standard model for the XML documents that can be different according to the different requirements.
HTML DOM is used to have a standard model used for the HTML documents having the properties and functions.

What is the use or function of XML DOM?

The XML DOM is used to define the standard model of the DOM structure and it defines all the properties of the XML elements or the methods for accessing it.
XML DOM is used to create the instance of the XML parser by using the standard interfaces like COM.
It consists of the inbuilt libraries and implementation code that is used to work with the document written in XML.
It uses the command CreateObject method to be used with the XML DOM that allows the creation of the Parser object.

The command that can be used in XML DOM is as follows:

Set objParser = CreateObject( “Microsoft.XMLDOM” )

What is the use or function of HTML DOM?

HTML DOM provides a way to implement the HTML document model by allowing it to extend the HTML: trees models.
It serves as both as HTML parser and uses the document class of HTML to apply the functions and properties in the same class.
The standard object model is created for the use of HTML and it provides a programming interface through which it can be recognized.
It provides platform independent and language independent features and properties that can be used.

What is the use of DOM in W3C standards?

HTML DOM is used to add, remove, and change the elements of HTML by using the HTML DOM.
DOM considers the entire element in an HTML document as a node and it treats all of them using the same standards.
The document is being given in the document node and all the elements of the HTML are present in the element node.
The text used in the HTML elements is for the text nodes and allows the properties to be used for further use.
HTML usually consists of the attribute and it is stored in the attribute node that allows easy modification of the properties.

Write a program that shows the use of DOM?

The root node is always written in HTML code <html> and the document nodes also mentioned in this node.
<html> consists of mostly two child nodes in the form of <head> and <body> and in <head> there is a sub-node that is present <title>.
<body> tag contains the node of the other tags that are used for visual representation of the content and it always stored in the text nodes.

The program that is used to represent the structure of the DOM:

<html>

<head>

<title>DOM Tutorial</title>

</head>

<body>

<h1>DOM Lesson one</h1>

<p>Hello world! </p>

</body>

</html>

What are the errors made while processing the DOM?

DOM is used to display the element node in the form of text using the text node and it shows the error while processing it.
The text element is stored in the text node and it is displayed like:

<title>DOM </title>, element node <title>

The tag is used to hold the text node with the value “DOM” that is used within it.
The value of the <title> tag is not the “DOM” but it allows the accessing of the text node using the HTML properties.
innerHTML property is being used to make the searching possible and allow the use of node properties.

What is the purpose of HTML DOM Node Tree?

HTML DOM view the HTML document with a tree structure format and it consists of root node and child nodes.
The node-tree is being accessed using the tree formation and the structure in which the elements get created.
The contents that are used being modified or removed using the new elements and it can be created within the limitations.
The structure consists of a document that is the root and within it Root element <html> from where the tree starts.
It consists of sub-elements like <head> and <body> and other text and attributes written in the HTML format.

How does the relationship exist between the node, child and siblings in node-tree?

Node tree consists of root node, child and siblings with a defined relationship with each other.
The relationship is described as such it allows the children on the same level to be called as siblings.
The root node is the top most nodes and through this node the accessing will be done and the elements will be communicated.
Every node in the tree will have exactly one parent node and root doesn’t have any parent in this.
A node at lower down the order can include many other nodes and they will be called as children of parent nodes.

Explain through program the relationship that exists between the root and other nodes present in node-tree?

The code that shows the relationship is as follows:

<html>

<head>

</head>

<body>

<p>Hello world!</p>

</body>

</html>

<html> is the top order node and can be termed as parent node or root node for more simplification.
Parent node is used to have the child nodes under them so the <html> consists of <head> and <body> as the child node.
<html> consists of two child nodes and <head> or other tags consists of other child nodes like that.
The <h1> element or <head> element or <title> element is being used for the child node and it allows the creation of more sub-nodes.

What is the programming interface used for DOM or HTML documents?

Programming interface is important if the DOM consisting of the HTML documents and provide settings for the node objects.
Nodes in the tree are allowed to access the programming interface and it is defined with the DOM properties and methods.
The properties and methods are used in the node and they are referred for the use in the HTML DOM.

The DOM property that exists in HTML:

x.innerHTML – this stores the text value of x used to display it on the x axis.

x.nodeName – this stores the node name of x on the x axis of the node.

x.nodeValue – this provides the value of x for the node that is being used.

What are the methods involved in HTML DOM?

HTML DOM methods are used as a way to generate the result without much of the written code and it can be easily used.

HTML DOM provides methods to simplify the tasks and the methods are as follows:

x.getElementById(id) – this allow the getting of the element that is associated with a specified id.

x.getElementsByTagName(name) – this gets all the elements using the tag name that is associated with it.

x.appendChild(node) – this inserts a child node to x and append the child node at the end of the tree.

x.removeChild(node) – this removes a child node from x and remove from the tree area also.

What are the properties of HTML DOM involved in the system?

innerHTML property is the property that allows easy modification of the content of an element in HTML.
It allows the returning or replacing of the content in HTML or the elements like <html> or <head> used by it.
It provides a way to use the page source and allows the way to dynamically modify those pages without manual effort.
The properties like id, class and other individual properties of an element is involved in writing the HTML code.

The example of it is shown below by using the <p> element properties as:

<html>

<body>

<p id=”intro”>Hello World!</p>

txt=document.getElementById(“intro”).innerHTML;

document.write(“<p>Hello world: ” + txt + “</p>”);

</script>

</body>

</html>

Write a program that uses Methods and properties of HTML DOM?

HTML DOM uses getElementById method in the JavaScript form to access the element’s id and make changes accordingly.

There are properties like childNodes and nodeValue used to get the content using an element.

<html>

<body>

<p id=”intro”>Hello World!</p>

txt=document.getElementById(“intro”).childNodes[0].nodeValue;

document.write(“<p>The text from the intro paragraph: ” + txt + “</p>”);

</script>

</body>

</html>

The use of innerHTML property being used by applying the learning method that is useful and easily understandable by the tree structure of DOM.

What are the different properties of Nodes?

Node is used in HTML DOM as an object that points to the other element in the tree and gets generated by the root node.

Nodes in an object form have some methods and properties that allow the accessing of the JavaScript to be used for modification.

The node properties include the following things:

nodeName: is in the read only format and it is the parameter that acts like a tag name. It provides the information of attribute node and other nodes.
nodeValue: is the way to specify the value of each individual node. The node value can be element wise or it can be text wise or other nodes value can be given.
nodeType: provides a way to return the type of the node used and that is also in the read only format.

Write a program to change an HTML element?

HTML DOM uses the JavaScript features, elements and properties to change the inner content of the HTML elements.
The HTML elements are having the attributes that are used to change the element’s properties like color, shape, etc.

The example that allows the change is as follows:

<html>

<body>

document.body.bgColor=”green”;

</script>

</body>

</html>

Write a program to change the HTML element using events?

Events are used to get generated when an action on a particular object takes place, this way some values gets changed or manipulated within a region.
Event handlers are used to handle the events and execute the code using which the event is occurring.
Events are usually being generated by the browser, when an event on some object takes place like user clicks an element.

The example is shown below that is used to change the HTML element values:

<html>

<body>

<input type=”button” onclick=”document.body.bgColor=’green’;”

value=”Change background color” />

</body>

</html>

What are the functionalities performed by onload() and onUpload()?

onload() and onUpload() are two functions that gets activated or the event gets triggered when the user enters or leaves the page.
onload() event is used to verify and check the user’s visit according to the browser’s type and it loads a version of the event.
It provides the web page information that allows easy access to the website and consists of the information regarding the event that is triggered.
Onload() and onUpload() events uses the cookies to hold down the values given by the users when it enters or leaves the page.

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