一个数组问题重复值合并问题

Question

constary=[{code:1,num:20,},{code:1,num:10,},{code:2,num:15,}]//怎样得出下面结果？constary=[{code:1,num:30,},{code:2,num:15,}]

Answer 1

constary=[{
code:1,
num:20
},{
code:1,
num:10
},{
code:2,
num:15
}]
functionmerge(list){
letresult=[]
letcache={}
list.forEach(item=>{
letkey=item.code
letindex=cache[key]
if(index!==undefined){
result[index].num+=item.num
}else{
result.push(Object.assign({},item))
cache[key]=result.length-1
}
})
returnresult
}
merge(list)
                            

Answer 2

functionmerge(arr){
letres={};
for(letitemofarr){
if(res[item.code])res[item.code].num+=item.num;
elseres[item.code]={code:item.code,num:item.num};//Avoidmodifyingtheoriginalobject.
}
returnObject.values(res);
}