check_sequence_numbers.js

function checkSequnceNumbers(target, counterLength= 6){
  // under es6
  // let sequentialCounter = Array.apply(null, Array(counterLength)).map(Number.prototype.valueOf,0);
  let sequentialCounter = new Array(counterLength).fill(0);
  let count = 0;
  
  for (let i = 0, len = target.length; i < len; i++) {
    let subCount = 0;
    
    for (let j = 1; j < len; j++) {
      if (target[j] === (target[i]+1)) {
        subCount = subCount + 1;
      } else {
        continue;
      }
    }
    
    count = count + subCount;
    if (subCount === 0) {
      sequentialCounter[count] = sequentialCounter[count] + 1;
      count = 0;
    }
  }
  
  return sequentialCounter;
}

let target = [1, 2, 3, 5, 6, 7, 8, 10, 11, 13, 16, 17];
console.log(checkSequnceNumbers(target));
// => [1, 2, 1, 1, 0, 0]