如果只想得到一個數(shù)組的話用 filter，如果想得到多個數(shù)組得用 reduce

const groupBy = (arr, fn) =>
  arr.map(typeof fn === 'function' ? fn : val => val[fn]).reduce((acc, val, i) => {
    acc[val] = (acc[val] || []).concat(arr[i]);
    return acc;
  }, {});

Object.values(groupBy(arr, 'projectId'))

let result=array.reduce(function(initArray,item){
    let index=item.productid;
    if(initArray[index]){
        initArray[index].push(item)
    }else{
        initArray[index]=[item]
     }
    return  initArray;
},[])
console.log(result)
方法多種多樣

var a = [{id: 1}, {id: 3}, {id: 2}, {id: 3}, {id: 1}];
var b = a.reduce((r, x) => ((r[x.id] || (r[x.id] = [])).push(x), r), {});
var c = Object.keys(b).map(x => b[x]);

console.log(c); // [[{id: 1}, {id: 1}], [{id: 2}], [{id: 3}, {id: 3}]]