Updating an object within an array of objects in Angular

Question

Updating an object within an array of objects in Angular

Imagine having a unique object array named itemArray with two items inside;

{
  "totalItems": 2,
  "items": [
    {
      "id": 1,
      "name": "dog"

    },
    {
      "id": 2,
      "name": "cat"
    },
    ]
}

If you receive an updated result for only id 2 through a subscription, how can you efficiently update the object array without looping through all items?

An ideal solution would be something like the following code snippet;

updateUser(user){
    this.myservice.getUpdate(user.id)
    .subscribe(newitem => {
      this.updateArray(newitem);
    });
}

  updateArray(newitem){
    this.itemArray.items[newitem.id].name = newitem.name
  }

Or even better, completely replacing the entire object;

  updateArray(newitem){
    this.itemArray.items[newitem.id] = newitem
  }

The provided example updates the array based on the index of the array. How can you instead update it based on newitem.id?

Template requested in comment:

<tr *ngFor="let u of itemsArray.items; let i = index">
  <td>{{ u.id }}</td>
  <td>{{ u.name }}</td>
  <td>
    <input type="checkbox" checked="u.accepted" [(ngModel)]="itemsArray.items[i].accepted" (ngModelChange)="updateUser(u)">
    <label for="singleCheckbox-{{i}}"></label>
  </td>
</tr>

angular typescript

Answer 1

Answer №1

Latest Update:

  updateItem(newItem){
    let index = this.itemsList.findIndex(item => item.id === newItem.id);
    this.itemsList[index] = newItem;

   // To trigger change detection in certain angular libraries, 
   // you may need to break the array reference like so:

   this.itemsList = Object.assign([], this.itemsList);
  }

View StackBlitz Demo

Previous Solution:

I've put together a Plunker demo based on your example that updates the object with matching newItem.id

Here's a snippet of the relevant function:

updateItem(newItem){
    let existingItem = this.itemsList.find(this.determineIndexToUpdate, newItem.id);

    let index = this.itemsList.indexOf(existingItem);

    this.itemsList[index] = newItem;
  }

  determineIndexToUpdate(newItem) { 
        return newItem.id === this;
  }

Answer 2

Latest Update:

  updateItem(newItem){
    let index = this.itemsList.findIndex(item => item.id === newItem.id);
    this.itemsList[index] = newItem;

   // To trigger change detection in certain angular libraries, 
   // you may need to break the array reference like so:

   this.itemsList = Object.assign([], this.itemsList);
  }

View StackBlitz Demo

Previous Solution:

I've put together a Plunker demo based on your example that updates the object with matching newItem.id

Here's a snippet of the relevant function:

updateItem(newItem){
    let existingItem = this.itemsList.find(this.determineIndexToUpdate, newItem.id);

    let index = this.itemsList.indexOf(existingItem);

    this.itemsList[index] = newItem;
  }

  determineIndexToUpdate(newItem) { 
        return newItem.id === this;
  }

Answer 3

Answer №2

Am I overlooking something by updating the item directly when it is passed as an argument?

updateItem(item){
  this.itemService.getUpdate(item.id)
  .subscribe(updatedItem => {
    item = updatedItem;
  });
}

UPDATE: If you have no other option but to iterate through your entire array to update the item, consider using findIndex :

let itemIndex = this.items.findIndex(item => item.id == retrievedItem.id);
this.items[itemIndex] = retrievedItem;

Answer 4

Am I overlooking something by updating the item directly when it is passed as an argument?

updateItem(item){
  this.itemService.getUpdate(item.id)
  .subscribe(updatedItem => {
    item = updatedItem;
  });
}

UPDATE: If you have no other option but to iterate through your entire array to update the item, consider using findIndex :

let itemIndex = this.items.findIndex(item => item.id == retrievedItem.id);
this.items[itemIndex] = retrievedItem;

Answer 5

Answer №3

Consider a different strategy:

const list = [{key:'abc1', title: 'abc'}, {key:'def2', title: 'def'}, {key:'ghi3', title: 'ghi'}];
const updatedItem = {key: 'abc1', title: 'Different technique'};

list.find(element => element.key === updatedItem.key).title = updatedItem.title;

Answer 6

Consider a different strategy:

const list = [{key:'abc1', title: 'abc'}, {key:'def2', title: 'def'}, {key:'ghi3', title: 'ghi'}];
const updatedItem = {key: 'abc1', title: 'Different technique'};

list.find(element => element.key === updatedItem.key).title = updatedItem.title;

Answer 7

Answer №4

Another option to update an existing object is as follows:

toDoList = [
                {id:'1234', name:'example'},
                {id:'5678', name:'example'},
                {id:'9012', name:'example'}
              ];

newTaskToUpdate = {id:'5678', name:'modified'};
this.toDoList.map((task, index) => {
         if (task.id == newTaskToUpdate.id){
            this.toDoList[index] = updatedTask;
          }
        });

Answer 8

Another option to update an existing object is as follows:

toDoList = [
                {id:'1234', name:'example'},
                {id:'5678', name:'example'},
                {id:'9012', name:'example'}
              ];

newTaskToUpdate = {id:'5678', name:'modified'};
this.toDoList.map((task, index) => {
         if (task.id == newTaskToUpdate.id){
            this.toDoList[index] = updatedTask;
          }
        });

Answer 9

Answer №5

Consider using the Array.forEach() function.

itemArray.forEach(item => {
    if (item.id === newItem.id) {
        item.name = newItem.name;
    }
});

Answer 10

Consider using the Array.forEach() function.

itemArray.forEach(item => {
    if (item.id === newItem.id) {
        item.name = newItem.name;
    }
});

Answer 11

Answer №6

I prefer designing a map

export class object{
    title: string; 
    code: string
}

let storage = new Map<string, object>();

then you can conveniently

this.storage[newobject.code] = newobject;

or

this.storage.set(newobject.code, newobject);

Who needs arrays anyway? :)

Answer 12

I prefer designing a map

export class object{
    title: string; 
    code: string
}

let storage = new Map<string, object>();

then you can conveniently

this.storage[newobject.code] = newobject;

or

this.storage.set(newobject.code, newobject);

Who needs arrays anyway? :)

Answer 13

Answer №7

To modify a single item, you can use the following example.

const chosenItem = itemList.find(selectedItem => selectedItem.id === id);

if (chosenItem) {
  chosenItem.title = 'new title';
}

Answer 14

To modify a single item, you can use the following example.

const chosenItem = itemList.find(selectedItem => selectedItem.id === id);

if (chosenItem) {
  chosenItem.title = 'new title';
}

Answer 15

Answer №8

updateDataValue(item){    
     // getting index from the item array
     let index = this.list.indexOf(item);
    // toggling a specific item in the list
     this.list[index].visible =  !this.list[index].visible;
}

Answer 16

updateDataValue(item){    
     // getting index from the item array
     let index = this.list.indexOf(item);
    // toggling a specific item in the list
     this.list[index].visible =  !this.list[index].visible;
}

Answer 17

Answer №9

One way to locate and modify an element is by employing a for loop:

updateItem(newData){
  for (let j = 0; j < this.dataArray.length; j++) {
      if(this.dataArray[j].key == newData.key){
        this.results[j] = newData;
      }
    }
}

Answer 18

One way to locate and modify an element is by employing a for loop:

updateItem(newData){
  for (let j = 0; j < this.dataArray.length; j++) {
      if(this.dataArray[j].key == newData.key){
        this.results[j] = newData;
      }
    }
}

Answer 19

Answer №10

One way to prevent object mutation in an array in Angular/TypeScript is demonstrated below.

For instance, using your item array as a BehaviorSubject:

// Initializing items$ with a default array
this.items$ = new BehaviorSubject<any>([user1, user2, ...])

updateUser(user){
   this.myservice.getUpdate(user.id).subscribe(newitem => {

     // Filtering out the old item
     const items = this.items$.value.filter((item) => item.id !== newitem.id);

     // Adding the newItem and updating the table
     this.items$.next([...items, newItem])
   });
}

To display the items in the template, you can subscribe to items$

<tr *ngFor="let u of items$ | async; let i = index">
   <td>{{ u.id }}</td>
   <td>{{ u.name }}</td>
   <td>
        <input type="checkbox" checked="u.accepted" (click)="updateUser(u)">
        <label for="singleCheckbox-{{i}}"></label>
   </td>
</tr>

Answer 20

One way to prevent object mutation in an array in Angular/TypeScript is demonstrated below.

For instance, using your item array as a BehaviorSubject:

// Initializing items$ with a default array
this.items$ = new BehaviorSubject<any>([user1, user2, ...])

updateUser(user){
   this.myservice.getUpdate(user.id).subscribe(newitem => {

     // Filtering out the old item
     const items = this.items$.value.filter((item) => item.id !== newitem.id);

     // Adding the newItem and updating the table
     this.items$.next([...items, newItem])
   });
}

To display the items in the template, you can subscribe to items$

<tr *ngFor="let u of items$ | async; let i = index">
   <td>{{ u.id }}</td>
   <td>{{ u.name }}</td>
   <td>
        <input type="checkbox" checked="u.accepted" (click)="updateUser(u)">
        <label for="singleCheckbox-{{i}}"></label>
   </td>
</tr>

Answer 21

Answer №11

Locate the specific item in the dataset and make necessary updates.

function updateRecord(identifier: any, newValue: any) {
    const position = this.DataCollection.findIndex((item) => item.id === identifier.id);

    console.log(position);
    
    if (position !== -1) {
        newValue.value.id = identifier.id;
        this.DataCollection[position] = newValue.value;
        const jsonData = JSON.stringify(this.DataCollection);
        localStorage.setItem('DataCollection', jsonData);
    } 
}

Answer 22

Locate the specific item in the dataset and make necessary updates.

function updateRecord(identifier: any, newValue: any) {
    const position = this.DataCollection.findIndex((item) => item.id === identifier.id);

    console.log(position);
    
    if (position !== -1) {
        newValue.value.id = identifier.id;
        this.DataCollection[position] = newValue.value;
        const jsonData = JSON.stringify(this.DataCollection);
        localStorage.setItem('DataCollection', jsonData);
    } 
}

Updating an object within an array of objects in Angular

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

Answer №7

Answer №8

Answer №9

Answer №10

Answer №11

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