How to change value of Object inside an Array?

Question

I want to change the values of the objects inside an array. I have created an object which I insert in every loop in an array.

If encountered with a missing value, I want to update the values of the existing object.

When the loop runs, it always enters the last object details from the api into the array.

Here; the screenshot: https://i.sstatic.net/n49Qc.png

var msg = data.message; // messages array from api
let body;
let posts = [];// empty array created

//object structure
let post ={
    id:'',
    desc: '',
    creator: '',
    time: '',
    likes: 0,
    attachment: '',
};
for(let i in msg){
    if(msg[i].body.includes(':')){ //if message body include object notation ':'
      body = JSON.parse(msg[i].body); // parse text message body into json
      if(body.contentDescription){ //if content is true
        post.id = body.postId; //id
        post.creator = body.createdUserName; //post creator
        post.time = body.publishedDate; //post publish date
        post.desc = body.contentDescription; //post content

        posts.push(post);
      }
      else if(posts.length > 1){
        for(let j in posts){
          if(posts[j].id === body.postId){
            console.log(posts[j].id);
            if(body.likeCount){ //if likeCount is true
              posts[j].likes += 1; //increase like count
            }else if(body.attachmentId){ //of Attachment is true
              posts[j].attachment = body.attachmentId; // update    attachement value
            }
          }
          break;
        }
      }


    }


};

Please help where am I doing it wrong?

Sample Data: i.imgur.com/jkXnrrG.png and Sample Result: i.imgur.com/wXx6T0t.png — Saumay Paul
– Saumay Paul, Commented Jan 7, 2019 at 11:56

Sergey Mell · Accepted Answer · 2019-01-07 11:32:31Z

1

Objects in JavaScript are sent via a link to the piece of memory. So when you change your post you are changing all the posts because all of them are looking to the same piece of memory.

You can change your code in a next way so it start working correct

...
if(body.contentDescription){ //if content is true
    let postItem = Object.assign({}, post); // Coping an object so breaking the memory link
    postItem.id = body.postId; //id
    postItem.creator = body.createdUserName; //post creator
    postItem.time = body.publishedDate; //post publish date
    postItem.desc = body.contentDescription; //post content

    posts.push(postItem);
  }
...

However, there is more than one way to skin a cat so this is not the only solution.

answered Jan 7, 2019 at 11:32

Sergey Mell

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3 Comments

Saumay Paul Over a year ago

Great!!! It's working to get me the ids correctly but I am not able to update the values if same ids are detected. Any suggestions??

Sergey Mell Over a year ago

It seems to me that break is not in the right place. It breaks the loop just after the first iteration. It should be one layer up to break after the duplicate was found.

Saumay Paul Over a year ago

I just used forEach() method in place of for-in and it worked!

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