Solution to 2D array problem from hackerrank in ES6 - https://www.hackerrank.com/challenges/2d-array/problem

HourGlass.js

#!/usr/bin/env node
// https://www.hackerrank.com/challenges/2d-array/problem

class HourGlass {
  constructor(attrs, debug) {
    this.attrs = attrs
    this.debug = debug
    this.value = this.compute()
  }

  compute() {
    if (this.debug) {
      console.log("attrs:", this.attrs)
      console.log("topRow:", this.topRow())
      console.log("middle:", this.middle())
      console.log("botRow:", this.botRow())
    }
    return this.topRow() + this.middle() + this.botRow()
  }

  topRow() {
    return this.attrs.topLeft + this.attrs.topMid + this.attrs.topRight
  }

  middle() {
    return this.attrs.mid
  }

  botRow() {
    return this.attrs.botLeft + this.attrs.botMid + this.attrs.botRight
  }
}


class Matrix {
  constructor(array, debug) {
    this.array = array
    this.debug = debug
  }

  findHourGlasses() {
    // 1 1 1 0 0 0
    // 0 1 0 0 0 0 <-- start at position 1,1 end at position 1,4
    // 1 1 1 0 0 0
    // 0 0 2 4 4 0
    // 0 0 0 2 0 0
    // 0 0 1 2 4 0
    let arr = this.array
    var maxHourGlass = {}
    for (var i = 1; i < arr.length - 1; i++) {
      let row = arr[i]
      for (var j = 1; j < row.length - 1; j++) {
        let hourGlass = new HourGlass({
          topLeft: arr[i-1][j-1],
          topMid: arr[i-1][j],
          topRight: arr[i-1][j+1],
          mid: arr[i][j],
          botLeft: arr[i+1][j-1],
          botMid: arr[i+1][j],
          botRight: arr[i+1][j+1],
          position: {y: i, x: j}
        })

        if (this.debug) console.log("compute:", hourGlass.value)
        if (!maxHourGlass.hasOwnProperty("value") || maxHourGlass.value < hourGlass.value) {
          maxHourGlass = hourGlass
        }
      }
    }
    return maxHourGlass
  }
}


// var matrix = [
//   [1,1,1,0,0,0],
//   [0,1,0,0,0,0],
//   [1,1,1,0,0,0],
//   [0,0,2,4,4,0],
//   [0,0,0,2,0,0],
//   [0,0,1,2,4,0]
// ]

// -6
var matrix = [
  [-1,-1, 0,-9,-2,-2],
  [-2,-1,-6,-8,-2,-5],
  [-1,-1,-1,-2,-3,-4],
  [-1,-9,-2,-4,-4,-5],
  [-7,-3,-3,-2,-9,-9],
  [-1,-3,-1,-2,-4,-5]
]

let hourGlassFinder = new Matrix(matrix)
console.dir(hourGlassFinder.findHourGlasses())