Proxy cool array methods

Here is a list of array operations that you can review, such as blitz.
From now on, we'll be working with these arrays.

const numbers: number[] = [0, 1, 2];
const alphabet: string[] = ['a', 'b', 'c'];

Indexing

numbers.indexOf(2) // 2
numbers.indexOf(10) // -1
numbers[5] // undefined
numbers[-1] // undefined
numbers[Infinity] // undefined
numbers['1'] // 1

Bonus tips (negative index)

numbers.at(-1); // 2, (builtin at method)

const coolNumbers = new Proxy(numbers, {
  get(target, props) {
    const index: number = +(<string>props)
    if (index < 0) 
      return Reflect.get(target, index + target.length)
    return Reflect.get(target, props)
  },
})
coolNumbers[-1] // 2

Cool operation on an array

flat, joining with tagged templates

// **flat** ES2019
const nested = [0, [1], [[2]], [[[3]]], [[[[4], 3], 2], 1]]
nested.flat() // [ 0, 1, [ 2 ], [ [ 3 ] ], [ [ [4], 3 ], 2 ], 1 ], default level  1
nested.flat(3) // [0, 1, 2, 3, [ 4 ], 3, 2, 1]
nested.flat(Infinity) // [0, 1, 2, 3, 4 , 3, 2, 1]

// joining
alphabet.join(',') // a,b,c
// @ts-ignore
alphabet.join`,` // a,b,c
alphabet.toString() // a,b,c

Make a similar cool python range method with proxy

/*  cool python range */
const range = (start: number, stop?: number, step?: number) => {
  if (step === undefined) step = 1
  if (stop === undefined) {
    stop = start
    start = 0
  }

  return Array.from(
    { length: (stop - start) / step },
    (_, i) => start + i * step!,
  )
}

for (const i of range(5, 10)) console.log(i)
// 5, 6, 7, 8, 9