Javascript: Array Sorting Guess output of the Code

Guess output of code.

Code

let arr =[1,21,30,4]

arr.sort((a,b)=>{

 return b-a

})

console.log(arr)

Here sorting will be done element are treated as number & sorting is descending.

output will be [ 30, 21, 4, 1 ]

let arr =[1,21,30,4]

arr.sort()

console.log(arr)

Here sorting will be done in lexographic order ascending where each element is trated as string

output will be [1,21,30,4]