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The correct choice is (B) DOMHighResTimeStamp

The best I can explain: The Performance.now() method returns a DOMHighResTimeStamp, MEASURED in milliseconds, ACCURATE to one thousandth of a millisecond EQUAL to the number of milliseconds since the PerformanceTiming.navigationStart property and the call to the method. The returned value represents the time elapsed since the time origin.

The correct choice is (d) domload

Easy explanation: PerformanceTiming.domComplete read-only property RETURNS an UNSIGNED long long representing the moment, in miliseconds since the UNIX epoch, when the parser finished its WORK on the main DOCUMENT. The following PROPERTIES are associated with the Processing event:

domComplete

domContentLoaded

domInteractive

domLoading

unLoadEnd.

The correct answer is (c) JSON.stringify

Best EXPLANATION: JSON.stringify does not SERIALIZE undefined values or FUNCTIONS within an object. JSON.stringify() converts a JavaScript object into a string.

Correct answer is (b) To identify the SCRIPTING language

Easiest explanation: A VARIABLE is created to HOLD whatever tag you create, and then branch the logic based on the value of type, which IDENTIFIES it’s for JavaScript or for CSS. Hence, the ATTRIBUTE acts as an identifier to the tag.

Right choice is (B) Date.Now() – performance.timing.domLoading

The explanation is: The rendering ENGINE parses the HTML and the CSS and displays the parsed content on the screen. The render time is calculated as Date.Now() – performance.timing.domLoading.

Correct choice is (c) Immediate LOADING is not necessary

Explanation: Lazy loading is a DESIGN PATTERN commonly used in COMPUTER programming to defer initialization of an object until the point at which it is needed. It can CONTRIBUTE to efficiency in the program’s operation if properly and appropriately used. Lazy loading is a kind of loading in which we don’t need our JavaScript code to be available as soon as the page loads.

Correct answer is (c) DATA.frame()

Easy EXPLANATION: A Data frame is a two-dimensional data structure, i.e., data is ALIGNED in a tabular fashion in rows and COLUMNS.

The CORRECT answer is (d) Any of the mentioned

To explain: The TYPE of script_url can be anything that will be compared with the typeof keyword’s result. The src ATTRIBUTE SPECIFIES the location (URL) of the external resource.

The correct CHOICE is (d) Sends it to the interpreter

The EXPLANATION: If the browser encounters a script tag without an src attribute, the rendering ENGINE SIMPLY PASSES the code to the JavaScript Interpreter for execution. The src attribute specifies the location (URL) of the external resource.

Right option is (a) Fetching data

Easy EXPLANATION: The LOADING attribute allows a browser to defer loading offscreen images and iframes until USERS scroll NEAR them. The CSS Lazy Loading is begun with fetching the JAVASCRIPT and the CSS files.

Correct answer is (b) Remove the SRC ATTRIBUTE

Best explanation: The way we WOULD lazy load images would be to ALTER the HTML of the page to remove the contents of the src attribute of each image. We could just move the contents of the src attribute to an attribute in the image tag of our own design, maybe the rel attribute.

Correct option is (c) getElementsbyTagName()

For explanation I would say: The getElementsByTagName() method returns a COLLECTION of all ELEMENTS in the document with the specified tag name, as a NodeList object. The method getElementsbyTagName() can be used to get a PARTICULAR value USING the tagged name associated with the document.

Correct option is (c) Event, Function

To EXPLAIN: The ADDEVENTLISTENER() method attaches an event handler to an element without OVERWRITING existing event handlers. The attachEvent function accepts two PARAMETERS: the event to attach to, and the function to INVOKE when the event occurs.

The CORRECT CHOICE is (c) 2

Easy explanation: The Window interface’s performance property returns a Performance OBJECT, which can be used to gather performance INFORMATION about the current document. There are totally 2 properties associated with the window.performance and they are:

navigation

type.

Correct choice is (d) PerformanceTiming

The EXPLANATION is: Performance.timing read-only PROPERTY RETURNS a PerformanceTiming OBJECT containing latency-related performance information. PerformanceTiming is an INTERFACE in JavaScript.

Correct choice is (c) Creates IMAGINARY node object

Explanation: The createDocumentFragment() METHOD creates a imaginary Node object, with all the PROPERTIES and methods of the Node object. DocumentFragments are DOM Nodes. They are NEVER part of the main DOM TREE.

Correct answer is (C) Boolean

For explanation I would say: The async attribute is a boolean attribute. When present, it specifies that the script will be EXECUTED asynchronously as soon as it is available. The async attribute OPTIONALLY accepts the boolean DATATYPE of default VALUE as true.

Right CHOICE is (b) Parse Content

Explanation: After retrieving the content in chunks, the contents will be PARSED. The Render ENGINE workflow contains:

Parse Content

Build DOM nodes in render tree

Layout positioning of DOM elements

Paint DOM elements.

The correct OPTION is (a) Tokens

Explanation: The string returned by the network layer GETS tokenized into meaningful chunks. The rendering ENGINE then takes the tokens and converts them to DOM elements. There are five categories of tokens: 1) constants, 2) IDENTIFIERS, 3) operators, 4) separators, and 5) reserved words.

Right option is (b) Complete ROUNDTRIP absent

The explanation is: HTTP redirects are significant because they cause a complete roundtrip for each redirect. The ORIGINAL REQUEST is RETURNED from the web server as either a 301 or a 302 with the path to the NEW location.

The CORRECT choice is (c) Navigation by moving back & forward through history

The BEST I can explain: The navigator object CONTAINS information about the browser. When the type attribute of the navigation object is set to 2, it means that the navigation is done by moving back or forward through history.

Right choice is (B) onload

For EXPLANATION: The onload event OCCURS when an object has been LOADED. The onload event occurs when an object has been loaded.

Right ANSWER is (a) ADDEVENTLISTENER()

The explanation: The addEventListener() method attaches an event handler to the specified element. The addEventListener() method is used to ADD an event LISTENER to the script.

Right answer is (c) TYPE_BACK_FORWARD

For explanation: TYPE_BACK_FORWARD performs NAVIGATION through a history traversal operation. TYPE_BACK_FORWARD: Has the value of 2, INDICATING that the PAGE was NAVIGATED to via the browser history, either USING the back or forward buttons or programmatically through the browser’s history object.

The CORRECT option is (b) 2

The best I can EXPLAIN: The NAVIGATOR object contains information about the browser. There are a TOTAL of 2 read-only attributes present in the navigator object namely:

redirectCount

type.

Correct answer is (b) loadEventEnd-responseEnd

For explanation I would say: The legacy PerformanceTiming.loadEventEnd read-only property RETURNS an unsigned LONG representing the MOMENT, in milliseconds since the UNIX epoch, when the load event handler terminated, that is when the load event is completed. The time TAKEN for PAGE load once the page is received from the server: loadEventEnd-responseEnd.

The correct answer is (C) both responseStart and responseEnd

The explanation is: PerformanceTiming.responseStart read-only property RETURNS an unsigned long long representing the moment in TIME (in milliseconds since the UNIX epoch) when the browser RECEIVED the first byte of the response from the server, cache, or local resource. The PROPERTIES associated with the Response event are:

responseStart

responseEnd.