How to separate each sub group in main group Array using javascript

Question

I have an Array. It contains several subgroups. Example:

let mainArray=[50,51,52,53,54,511,512,513,514,521,522,523,524,525,526,527]

I want

Answer 1

var arr = [50,51,52,53,54,511,512,513,514,521,522,523,524,525,526,527];
var result = [],
    lastVal = -1;
while(arr.length) {
  var currentIndex = arr.length - 1;
  var currentValue = arr[currentIndex];
  var c = Math.floor(currentValue/10);
  if (c !== lastVal) {
    lastVal = c;
    result.push([currentValue]);
  }else{
    result[result.length-1].push(currentValue);
  }
  arr.splice(currentIndex, 1);
}
result.forEach(function(arr){ arr.reverse(); });
console.log(result);

Answer 2

Here's a solution using Ramda.js

const x = [50,51,52,53,54,511,512,513,514,521,522,523,524,525,526,527]

const f = R.pipe(
  R.sortBy(R.identity), 
  R.groupWith(R.pipe(R.subtract, Math.abs, R.equals(1)))
)

console.log(f(x))

<script src="//cdnjs.cloudflare.com/ajax/libs/ramda/0.25.0/ramda.min.js"></script>

Answer 3

Use the Array reduce function :

let mainArray=[50,51,52,53,54,511,512,513,514,521,522,523,524,525,526,527];

let groups = mainArray.reduce ( 
  (grps, el, i, main) => ((el === main[i-1] + 1 ? grps[0].push (el)
                                                : grps.unshift ([el])), grps), []);

[sub3, sub2, sub1] = groups;

console.log (sub1, sub2, sub3);

Answer 4

This will create an Array of Subarays:

const arr = [50,51,52,53,54, 511,512,513,514, 521,522,523,524,525,526,527];
let newArr = [];
let temp = [arr[0]];

for (let index = 1; index < arr.length; index++) {
  if (arr[index] == arr[index - 1] + 1) {
    temp.push(arr[index]);
  } else {
    newArr.push(temp);
    temp = [];
  }
  
  if (index == arr.length - 1) {
    newArr.push(temp);
  }
}

console.log(newArr)