Web Development JavaScript 4

Question 1

What is the output of `console.log([] + [])`?

Accepted Answer

""

Answer

Both arrays are coerced to empty strings, and string concatenation produces an empty string `""`.

Question 2

Which of the following correctly uses destructuring to extract values from an object?

Accepted Answer

const {name, age} = person;

Answer

Object destructuring uses curly braces to extract named properties into variables.

Question 3

What does `event.stopPropagation()` do in JavaScript?

Accepted Answer

Stops the event from bubbling up to parent elements

Answer

`stopPropagation()` halts the event from traveling up (or down) the DOM tree after the current handler executes.

Question 4

What is a JavaScript generator function?

Accepted Answer

A function declared with `function*` that can pause and resume execution using `yield`

Answer

Generator functions use `function*` syntax and `yield` to produce a sequence of values on demand, pausing execution between yields.

Question 5

What does `localStorage.setItem('key', value)` do when `value` is an object?

Accepted Answer

Stores `[object Object]` as a string

Answer

`localStorage` only stores strings, so objects are coerced via `.toString()`, producing `[object Object]` unless you manually call `JSON.stringify()`.

Web Development Practice Test

Web Development Practice Test

Web Development JavaScript 4