JSON

Question 1

What is JSON?

Answer 1

JSON is JavaScript Object Notation

Question 2

What are serialization and deserialization?

Answer 2

Serialization is the process of turning an object in memory into a stream of bytes so you can do stuff like store it on disk or send it over the network.

Deserialization is the reverse process: turning a stream of bytes into an object in memory.

Question 3

Why are serialization and deserialization useful?

Answer 3

to send data that servers can understand

Question 4

How do you serialize a data structure into a JSON string using JavaScript?

Answer 4

JSON.stringify()

Question 5

How do you deserialize a JSON string into a data structure using JavaScript?

Answer 5

JSON.parse()

Question 6

How do you store data in localStorage?

Answer 6

localStorage.setItem(““key””, ““value””) (Must be JSON string)

Question 7

How do you retrieve data from localStorage?

Answer 7

localStorage.getItem(““key)

Question 8

What data type can localStorage save in the browser?

Answer 8

Note that you can only store JSON strings in localStorage. (On Firefox and Chrome, the localStorage data is stored inside a Sqlite database.) If you want to keep arrays or objects, a straightforward way is to convert the data to JSON using the JSON. stringify method.

Question 9

When does the ‘beforeunload’ event fire on the window object?

Answer 9

The beforeunload event is fired when the window, the document and its resources are about to be unloaded. The document is still visible and the event is still cancelable at this point.