find substes

let subsets = 'abcd';

printSubsets(subsets);

function printSubsets(subsets, prefix='') {
    let subsetLength = subsets.length;
    
    if (prefix.length > 0) {
      console.log(prefix);
    }
    
    for (let i=0; i<subsetLength; i++) {
      printSubsets(subsets.substring(i+1, subsetLength), prefix + subsets[i]);
    }
}