text: 
  const _memUsage = map => JSON.stringify([...map]).length;
  
  let m = new Map();
  
  m.set('a', 1);
  m.set('b', { a: 1, b: 2, c: 3 });
  m.set('c', [1, 2, 3, 4, 5, 6]);
  
  console.log('before', process.memoryUsage().heapUsed / 1024 / 1024);
  for (let index = 0; index < 100000; index++) {
    m.set(index, { a: 1, b: 2, c: 3 });
  }
  console.log('after', process.memoryUsage().heapUsed / 1024 / 1024);
  const n = [
    2, 2, { a: 1 }, 2, 2
  ];
  
  console.log(_memUsage(m));
  console.log('after calc', process.memoryUsage().heapUsed / 1024 / 1024);
  
  // m.clear();
  m = null;
  console.log(m);
  console.log('after clear', process.memoryUsage().heapUsed / 1024 / 1024);
  // console.log(Buffer.from(n));