REST response compressing

compress.js

function compress(objects) {
  const fieldsSet = {};
  for (let i = 0; i < objects.length; i++) {
    const keys = Object.keys(objects[i]);
    for (let j = 0; j < keys.length; j++) {
      fieldsSet[keys[j]] = 1;
    }
  }
  
  const fields = Object.keys(fieldsSet);
  
  const entries = [];
  for (let i = 0; i < objects.length; i++) {
    const obj = objects[i];
    const entry = [];
    for (let j = 0; j < fields.length; j++) {
      entry.push(obj[fields[j]]);
    }
    
    entries.push(entry);
  }
  
  return {
    fields,
    entries
  };
}

decompress.js

function decompress({fields, entries}) {
  const objects = [];
  for (let i = 0; i < entries.length; i++) {
    const entry = entries[i];
    const obj = {};
    for (let j = 0; j < fields.length; j++) {
      obj[fields[j]] = entry[j];
    }
    
    objects.push(obj);
  }
  
  return objects;
}