JavaScript Modules 5

Question 1

What is tree shaking in the context of ES modules?

Accepted Answer

Dead-code elimination of unused exports by bundlers

Answer

Tree shaking leverages ES module static structure to detect and remove unused exports, reducing bundle size.

Question 2

What does `export { foo as default }` accomplish?

Accepted Answer

Makes `foo` the default export of the module

Answer

`export { foo as default }` is equivalent to `export default foo` and designates `foo` as the module's default export.

Question 3

Which statement correctly describes live bindings in ES modules?

Accepted Answer

Imported bindings reflect the current value of the export, even if it changes after import

Answer

ES module exports are live bindings, meaning the imported name always reflects the latest value of the exported variable.

Question 4

What is the purpose of the `modulepreload` link relation?

Accepted Answer

Instructs the browser to fetch and parse an ES module early to improve performance

Answer

`<link rel="modulepreload">` tells the browser to fetch, parse, and compile an ES module in advance, reducing latency.

Question 5

What error occurs if you try to assign to an imported binding?

Accepted Answer

A SyntaxError at parse time because imports are read-only

Answer

Imported bindings are read-only; attempting to assign to them causes a SyntaxError during parsing.

JavaScript Practice Test