Encountered a problem when attempting to instantiate an array of objects in Angular using TypeScript

Question

Encountered a problem when attempting to instantiate an array of objects in Angular using TypeScript

Encountering an Angular object-array creation error. The structure of the data I need to display is as follows:

stats : [
    {
        name : 'x', 
        age : 20
    },
    {
        name : 'y', 
        age : 10
    },
];

In my Angular code, I have defined it like this:

stats: Array<{ name: string,  age : number }> = [];

However, when attempting to assign a value like this:

this.stats[0]['name'] = 'x';

An error is thrown:

ERROR TypeError: Cannot set property 'name' of undefined

Note: I am not looking for an alternative solution as this specific representation and data binding are necessary for my project. Additionally, I cannot predefine the 'stats' array due to its dynamic nature and unknown size.

javascript arrays angular typescript object

Answer 1

Answer №1

info: Array<{ title: string, category : number }> = [];

This code snippet signifies the creation of an array containing anonymous objects, each with a title and a category property.

If you wish to set 'x' as the title for the first element, you can do so by writing:

this.info[0] = { title: 'x', category: 1 };

To make the age property optional, you can define it like this:

info: Array<{title: string, category?: number}> = [];

A question mark has been included to denote optionality. It is commonly recommended to define a named object and declare your array in this manner:

info: Info[];

That's how I was taught, at least.

Answer 2

info: Array<{ title: string, category : number }> = [];

This code snippet signifies the creation of an array containing anonymous objects, each with a title and a category property.

If you wish to set 'x' as the title for the first element, you can do so by writing:

this.info[0] = { title: 'x', category: 1 };

To make the age property optional, you can define it like this:

info: Array<{title: string, category?: number}> = [];

A question mark has been included to denote optionality. It is commonly recommended to define a named object and declare your array in this manner:

info: Info[];

That's how I was taught, at least.

Answer 3

Answer №2

Create an Interface and initialize your object before Associating it

export class AppComponent  {

     data:Array<Iinfo>=[];
     constructor(){
       this.data[0]={title:'Example',number:5}
       console.log(this.data[0].title)
       console.log(this.data[0].number)
     }

    }

    export interface Iinfo{
      title:string,
      number:number,
    }

Associating with input field

 <input type="text" [(ngModel)]="data[0].title">

View Live Example on StackBlitz

Answer 4

Create an Interface and initialize your object before Associating it

export class AppComponent  {

     data:Array<Iinfo>=[];
     constructor(){
       this.data[0]={title:'Example',number:5}
       console.log(this.data[0].title)
       console.log(this.data[0].number)
     }

    }

    export interface Iinfo{
      title:string,
      number:number,
    }

Associating with input field

 <input type="text" [(ngModel)]="data[0].title">

View Live Example on StackBlitz

Encountered a problem when attempting to instantiate an array of objects in Angular using TypeScript

Answer №1

Answer №2

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