selectionSortLoopInvariant.js

const checkLoopInvariant = (newArray, originalArray, index) => {
  newArray = newArray.slice(0, index)
  originalArray = originalArray.sort((a,b) => a > b ? 1 : - 1).slice(0,index)

  if (index === 0) return true //no elements sorted yet

  for (let i = 0; i < newArray.length; i++) {
    if (!originalArray.includes(newArray[i])) {
      console.warn(`Error! ${newArray[i]} not one of the ${index} smallest elements`)
    }

    if (i < newArray.length - 1 && newArray[i] > newArray[i+1]) {
      console.warn(`Error! New Array is not properly sorted`)
    }
  }
}