Run Length Encoding.js

function rlEncode(str) {
  var strs = str.split('');
  var a1 = strs.reduce((acc, i) => {
    if (i === acc.cur) {
      return {
        cur: i,
        count: acc.count+1,
        s: acc.s
      }
    } else {
      return {
        cur: i,
        count: 1,
        s: acc.s + acc.cur + acc.count
      }
    }
  }, {cur: strs[0], count: 0, s: ''});
  
  return a1.s;
}