There are 3 ways to convert set to array:

Method 1:

using spread operator

let myset =new Set([1,2,3,4,5])

let myarr=[...myset]

console.log(myarr)

Method 2:

using Array.From()

let myset =new Set([1,2,3,4,5])

const myarr = Array.from(myset);

console.log(myarr)

Method 3:

using for loop

let myset =new Set([1,2,3,4,5])

const myarr = []

myset.forEach(x=>myarr.push(x))

console.log(myarr)

There are  4 ways to empty array:

method 1 (set length of variable as 0)

ex:

let arr=[1,2,3,4,5,6] 

arr.length=0 

console.log(arr)
output: []

Method 2 (Assign empty array to variable)

ex: 

let arr=[1,2,3,4,5,6]
arr=[];
console.log(arr)
output:
[]

Method 3 (Using splice)

let arr=[1,2,3,4,5,6] 

arr.splice(0,arr.length) 

console.log(arr)

output:

[]

Method 4 (by popping)

let arr=[1,2,3,4,5,6]
while(arr.length > 0) {
arr.pop();
}

console.log(arr)

 output: []

short answer: 

use JSON.stringify()

There are 3 ways to use this:

JSON.stringify(value, replacer)

JSON.stringify(value)
JSON.stringify(value, replacer)

JSON.stringify(value, replacer, space)

Below is demonstration

JSON.stringify(value)
// convert obj to json
ex:
let obj={"name": "srikanth", age:26, phoneNo:9321234576}
let jsonObj=JSON.stringify(obj)
console.log(jsonObj)

output:
{“name”:”srikanth”,”age”:26,”phoneNo”:9321234576}

JSON.stringify(value, replacer)
( to select keys in object)

let obj={"name": "srikanth", age:26, phoneNo:9321234576}

let jsonObj=JSON.stringify(obj,["name","age"])
console.log(jsonObj)

output:
{“name”:”srikanth”,”age”:26}

JSON.stringify(value, replacer, space)
 (to format output of stringified json)

let obj={"name": "srikanth", age:26, phoneNo:9321234576}
let jsonObj=JSON.stringify(obj,null,' ')
console.log(jsonObj)

output:
{
“name”: “srikanth”,
“age”: 26,
“phoneNo”: 9321234576
}