元素分组

通过 reduce 分组

---

function groupBy(objectArray,property){
  return objectArray.reduce(function(accumulator,currentValue,index,arr){
    const key = currentValue[property];
    if(!accumulator[key]){
      accumulator[key] = [];
    }
    accumulator[key].push(currentValue);
    return accumulator;
  },{});
}
const array = [
  { name: "Alice", age: 21 },
  { name: "Max", age: 20 },
  { name: "Jane", age: 20 },
];
const result = groupBy(array,'age');
console.log(result);