如何用for循环修改对象键更具声明性？

Question

I want to search through an existing object and modify its property. This works great:

function changeObjectKey(targetObject) {
       for(var i = 0; i < listofobjects.length; i++) {
          if(targetobject.keyone == listofobjects[i].keyone) 
            listofobjects[i].keytwo = 'changedvalue';
            break;
          }
        }
}

I want to make it smarter using filter, how can I do that? I tried:

function changeObjectKey(targetObject) {
let filteredobject = listofobjects.filter(function(currentobject) {
return (currentobject.keyone == targetobject.keyone);
 });
filteredobject.keytwo = 'changedvalue';

}

Note: Only a single object will match in the filter. Though the latter is not changing listofobjects.keytwo... but I think a copy of it. Whereas in the first case, the original listofobjects[i].keytwo is being changed.

What is the correct way to do this?

Answer 1

Just take the first [0] :

let filteredobject = listofobjects.filter(function(currentobject) {
return (currentobject.keyone == targetobject.keyone);
 })[0];
filteredobject.keytwo = 'changedvalue';

Answer 2

I guess map would be a better fit for this. Of course you could chain the map after a filter .

Also, I have not mutated the original object. If that is something you want to do you could do that. But generally, you do not use these function ( map , filter , reduce ) to mutate data.

function changeObjectKey(targetObject) {
  return listofobjects.map(function (obj) {
    if (obj.keyone !== targetobject.keyone) {
      return obj;
    }

    return Object.assign({}, obj, {
      keytwo = 'changedvalue'
    })
  })
}

Answer 3

I think is better the map() method.

The map() method creates a new array with the results of calling a provided function on every element in this array.

  listofobjects = listofobjects.map(function(currentobject) {
       if(currentobject.keyone === targetobject.keyone){
             currentobject.keytwo = "changed value";
       }
  });

The result is the same array, but now the keytwo of the tarjetobjec has change its value.