Find the number of ways to climb N number of stairs. (DP)

NumberOfWaysToClimbNStairs.js

const hashMap = {}

function countNumberOfWays (steps) {
  if (steps <= 0) {
    return 0
  } else if (steps === 1) {
    return 1
  } else if (steps === 2) {
    return 2
  } else {
    if (hashMap.hasOwnProperty(steps)) {
      return hashMap[steps]
    } else {
     const val = countNumberOfWays(steps - 1) + countNumberOfWays(steps - 2)
     hashMap[steps] = val
     return val
    }
  }
}

console.log(countNumberOfWays(4))