Q
Which of the following is a recommended practice for optimizing JavaScript performance?

Answer & Solution

Answer: Option A
Solution:
Minifying and concatenating scripts reduces file size and HTTP requests, optimizing JavaScript performance. Including all scripts in the <head> can lead to longer page load times, whereas synchronous loading can block rendering and affect performance negatively.
Related Questions on Average

Variables declared in the <body> section of an HTML document have what scope by default?

A). Local to the script or function.

B). Global throughout the document.

C). Limited to the <body> section.

D). Not accessible in JavaScript.

Which attribute is used to make an external JavaScript file load and execute after HTML parsing but before the DOMContentLoaded event in the <head> section?

A). async

B). defer

C). sync

D). load

When using an external JavaScript file in the <head> section with the defer attribute, when does it get executed?

A). After the HTML content is fully parsed.

B). Before the HTML content is parsed.

C). As soon as it starts loading.

D). After all other scripts in the <head>.

Placing JavaScript at the end of the <body> section is beneficial for:

A). Improving page load speed.

B). Blocking page rendering.

C). Increasing script complexity.

D). Hiding script functionalities.

Using the defer attribute with an external script in the <head> section means that the script:

A). Loads and executes after HTML parsing.

B). Loads synchronously with HTML parsing.

C). Loads and executes before HTML parsing.

D). Loads but doesn't execute.

Variables declared in the <head> section of an HTML document are accessible:

A). Globally throughout the document.

B). Only within the <head> section.

C). Only after the page has fully loaded.

D). Nowhere in the document.

Placing JavaScript at the end of the <body> section of an HTML document can result in:

A). Faster initial page rendering.

B). Slower overall page loading.

C). No impact on page performance.

D). Delayed execution of JavaScript.

What is the advantage of placing JavaScript at the end of the <body> section for non-critical scripts?

A). Faster initial page rendering.

B). Slower page load overall.

C). Better script execution order.

D). Increased script complexity.

What happens if JavaScript code in the <body> section of an HTML document is placed before critical content such as headings or main paragraphs?

A). It may cause FOUC (Flash of Unstyled Content).

B). It has no effect on page rendering.

C). It improves page load speed.

D). It slows down script execution.

What is the purpose of using the async attribute with an external JavaScript file?

A). To load the script asynchronously.

B). To defer script execution.

C). To block rendering until script loads.

D). To ensure script execution order.

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