问是否有一种方法可以创建以公共值作为键的对象，并将公共对象赋值为数组值？

EN

var data = [{
    a: 1,
    b: 2
  },
  {
    a: 2,
    b: 4
  },
  {
    a: 1,
    b: 6
  },
  {
    a: 2,
    b: 9
  }
];

function sortData() {
  var sortedData = {};
  data.forEach(sample => {
  // Need to check if the array for the sample has been created since we cannot "push" to "undefined".
    if (sortedData[sample.a]) {
      sortedData[sample.a].push(sample);
    } else {
      sortedData[sample.a] = [sample];
    }
  });
  return sortedData;
}

console.log(sortData());