How does `Array.from({length: 5}, (v, i) => i)` work?

Question

I may be missing something obvious here but could someone breakdown step by step why Array.from({length: 5}, (v, i) => i) returns [0, 1, 2, 3, 4]

Answer 1

The 2nd argument in the arrow function is always the index with Array.from() method 
    x=Array.from({length:5},(v,i,k)=>k)
console.log(x)
//Expected output Array(5) [ undefined, undefined, undefined, undefined, undefined ]
    x=Array.from({length:5},(v,i,k)=>v)
console.log(x)
//Expected output Array(5) [ undefined, undefined, undefined, undefined, undefined ]
    x=Array.from({length:5},(v,i,k)=>i)
console.log(x)
//Expected output Array(5) [ 0, 1, 2, 3, 4 ]
x=Array.from({length:5},()=>[])
//Expected Output Array(5) [ [], [], [], [], [] ]
x=Array.from({length:5},()=>{})
//Expected Output Array(5) [ undefined, undefined, undefined, undefined, undefined ]