[Javascript] Use a custom sort function on an Array in Javascript

Sorting in Javascript with sort uses lexical sorting by default, which means it will sort in alphabetical order. That's fine for strings of characters, but it means that arrays of numbers don't sort in numerical order! To fix that, we'll pass a custom comparator function to sort. The function you pass to sort will be passed two values from the array at a time, and should return a value <0, =0 or >0, based on which value should be sorted first in the final array.

Once you have a custom sort function implemented, you can sort in any way that you'd like. We'll show that by pulling out just part of a string, and sorting based on that value.

 

const numberArr = [12, 50, 6, -1, 0, -9]

const descSort = numberArr.sort((a, b) => {
  return b - a
})

console.log(descSort)


const numberSorted = numberArr.sort((a, b) => {
  if(a < 0 && b < 0) {
    return a - b  // -n should be start from small to large
  } else if(a < 0 || b < 0) {
    return b - a // +n come first, -n come last
  } else {
    return a - b // from small to large
  }
})

console.log(numberSorted) // [0, 6, 12, 50, -9, -1]


const floorArr = [
  "6th Floor",
  "2nd Floor",
  "11th Floor",
  "8th Floor",
  "7th Floor",
  "9th Floor",
  "1st Floor",
  "3rd Floor",
  "10th Floor",
  "5th Floor",
  "4th Floor",
]

const sorted = floorArr.sort((a, b) => {
  return a.match(/\d+/) - b.match(/\d+/)
})

console.log(sorted)  // ["1st Floor", "2nd Floor", "3rd Floor", "4th Floor", "5th Floor", "6th Floor", "7th Floor", "8th Floor", "9th Floor", "10th Floor", "11th Floor"]

[0, 6, 12, 50, -9, -1]