Compress string: ABBCCCD -> AB2C3D

compressString.js

function CompressString(str) {
	let acc = 0;
	let char;

	let result = str.split('').reduce((r, currentValue, index, arr) => {
	  if (currentValue != arr[index-1]) {
	      if (char) {
	          r += ((acc > 1) ? `${char}${acc}` : char);   
	      }
	    
	      char = currentValue;
	      acc = 0;
	  }

	  acc++;
	  return r;
	  
	}, '');

	result += char + ((acc > 1) ? acc : '');
	return result;
}
const str = 'AVVVBBBVVXDHJFFFFDDDDDDHAAAAJJJDDSLSSSDDDD';
console.info("Compression of string: ", CompressString(str));