Which javascript methods can be used to serialize an object into a string and deserialize a JSON string into an object, respectively?

Which JavaScript method can be used to serialize an object into a string and deserialize a JSON string into an object, respectively?

Refer to the code below
let inArray = [[1,2],[3,4,5]];
which two statements results in the array [1,2,3,4,5]?
choose 2 answer

Cloud Kicks has a class to represent items for sale in an online store, as shown below:
Class Item{
constructor (name, price){
this.name = name;
this.price = price;
}
formattedPrice(){
return 's' + String(this.price);}}
A new business requirement comes in that requests a ClothingItem class that should have all of
the properties and methods of the Item class but will also have properties that are specific to
clothes.
Which line of code properly declares the clothingItem class such that it inherits from
Item?

A developer is required to write a function that calculates the sum of elements in an array but is getting undefined every time the code is executed. The developer needs to find what is missing in the code below.
Const sumFunction = arr => {
Return arr.reduce((result, current) => {
//
Result += current;
//
), 10);
);
Which option makes the code work as expected?