Invocation And Performance Navigation — Part 2 MCQs with Explanations

When the browser parses the HTML markup, it stops rendering the HTML when it encounters an inline JavaScript block or external JavaScript file. At this point, the user experiences rendering delays. Moving the JavaScript to the end of the HTML markup would completely eliminate these pauses in rendering.

The rendering engine handles painting the content to the screen. When it encounters JavaScript, it hands it off to the JavaScript interpreter.

The rendering engine handles painting the content to the screen. When it encounters JavaScript, it hands it off to the JavaScript interpreter.

The JavaScript Interpreter runs the JavaScript code.

he network layer retrieves the content from the network.

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.

All of the mentioned belongs to the Render Engine work flow. The Render engine work flow contains : 1. Parse Content 2. Build DOM nodes in render tree 3. Layout positioning of DOM elements 4. Paint DOM elements.

After retrieving the content in chunks, the contents will be parsed.

After executing the script, the DOM nodes will be built in the render tree.

If there were no script tags, the DOM nodes will be built in the render tree.

The script loading loads remote JavaScript files programmatically and allows us to trick the rendering engine.

If the browser encounters a script tag without a src attribute, the rendering engine simply passes the code to the JavaScript Interpreter for execution.

The solution to the absence of a script tag without an src attribute is to create inline JavaScript to append script tags to the document dynamically

The method getElementsbyTagName() can be used to get a particular value using the tagged name associated with the document.

The type of the script_url can be anything that will be compared with the typeof keyword’s result.

The async option is a native attribute that will tell the browser to load the script asynchronously.

When using async you don’t know when the file will be downloaded, so you can attach an onload event handler to the script tag. This will allow you to invoke or instantiate any code that will need to be run when the file is downloaded:

The startTimeLogging() method captures the timing data for ad hoc, etc for referencing an uncached document.location.

The async attribute optionally accepts the boolean datatype of default value as true.

The createElement() can be used to create an element in the HTML DOM.

The createDocumentFragment() method creates a imaginary Node object, with all the properties and methods of the Node object.

The async attribute optionally accepts a boolean value and by default holds the value true.

The method to create a data frame is data.frame().

You can create a data frame to hold the mean page render times for each test URL, and a data frame to hold the mean load time for each test URL.

The property navigator.appCodeName is the same in both Netscape and IE.

The getSelection() method returns the value of the cursor-selected text.

Client-side JavaScript objects refer to objects that are available within the browser environment and interact directly with the user or the browser's document model. Option A: Database - This is not a client-side JavaScript object. Databases are typically managed server-side or through external services. Option B: Cursor - This is not a client-side JavaScript object. While cursors are used in database operations, they are not part of the JavaScript object model in the browser. Option C: Client - This is the correct answer. Client-side JavaScript objects include the browser's window, document, navigator, and other objects that interact directly with the user's interface. Option D: FileUpload - This is not a standard client-side JavaScript object. File uploads are handled via HTML input elements and server-side processing, though JavaScript can interact with these elements. Conclusion: In JavaScript, client-side objects are those that interact directly with the browser environment and user interface. Among the given options, only the Client is a client-side JavaScript object, making Option C the correct answer. Other options like Database , Cursor , and FileUpload are not considered standard client-side JavaScript objects.

The method localeCompare() returns a number indicating whether a reference string comes before or after or is the same as the given string in sort order.

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.

When we don’t need our JavaScript code to be available as soon as the page loads, we can script-load our external JavaScript after the window.onload event.

The attachEvent function accepts two parameters: the event to attach to, and the function to invoke when the event occurs.

If you try to make the call to perfLogger.showPerformanceMetrics() and the script hasn’t just loaded but also executed, then you will get an error.

Only onload is an attribute to the script object.

The addEventListener() method is used to add an event listener to the script.

The domLoading attribute is used when the document begins to load.

The render time is calculated as Date.Now() – performance.timing.domLoading.

The CSS Lazy Loading is begun with fetching the JavaScript and the CSS files.

A variable is created to hold whatever taag you create, and then branch the logic based on the value of type, which identifies it’s for JavaScript or for CSS.

The appendChild() method appends a node as the last child of a node.

Since the type of file is CSS, the type attribute should hold the value text/css.