Can you explain the significance of this line of code: elements:Array<any>?

Completely new to Angular and Javascript. I recently received an assignment for my angular.js class where I need to work on a code hint and make a simple form. The code hint provided is as follows:

export class AppComponent {
      items:Array<any>
      constructor() {
          this.items = [];
          this.addItems();
      }

I'm having trouble understanding the "items:Array" part and how it functions. How can I go about creating a basic form? Whenever I attempt to make changes, my app.module.ts stops working, which has never been an issue before.

This is what I have so far:

@Component({
  selector: 'app-root',
  template: `
    <h1> First Name: <input [(ngModel)]="items"> </h1>
    <ul *ngFor="let item of items;let i = index">
    <li>{{i}}: {{item.num}} <input type='button' value='delete' (click)=removeItem(item)></li>
    </ul>
  `,
})

Answer №1

Using TypeScript instead of JavaScript this time means that everything you write gets compiled into JavaScript before execution.

items:Array<any>

By declaring the type here, TypeScript understands that the items variable is of Array type, indicating it can only refer to an array and nothing else.

items:Array<any>=[]
items:Array<any>=new Array<any>();

If you attempt to assign something different:

items:Array<any>=2

The TypeScript compiler will throw an error indicating that a number type cannot be set to an array type.

<any>

This is a generic type declaration. By using "any", you are specifying that any type of item can be inserted into this array - numbers, strings, objects, arrays, etc. Thus, you could initialize it like this:

items:Array<any>=["Hello",2,{first:"user1",last:"pass1"},[4,6,7]];

However, if you specify a specific type like:

items:Array<number>;

It signifies that only numbers can be contained within that array. If an attempt is made to add something else, the compiler will signal an error stating that only numbers are allowed in a number type array.

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