Obtaining a return value from a function in Angular

After just starting to work with Angular, I am attempting to extract a value from a button displayed in the HTML using a function.

`<button class="btn" id="btn-gold"   (click)="value(9)"              
name="mybutton" value="9">`
9

I have also included the function call in the HTML file as follows: {{ value() }}.

This is my implementation in the .ts file:

public value(a) {
    console.log(a);
    return a;
    }

Unfortunately, despite seeing the number in the console, I am unable to display any values in my HTML file. The console shows:

  • 7
  • scoring.component.ts:18 undefined
  • scoring.component.ts:18 undefined

Now, my question is why can I not see the value in my .html file when it appears in the console? Additionally, why do I receive two undefined values per click?

Cheers, ArcherMark

Answer №1

Creating a TypeScript property with a value

propertyValue: number;

Implementing a function to set the property value

setValue(propertyValue: number) {
  this.propertyValue = propertyValue;
}

Utilize a button in the template to update the property value

<button class="btn" id="btn-silver" (click)="setValue(7)" name="mybutton" value="7">

Display the property value using template binding

{{ propertyValue }}

Answer №2

By utilizing {{ value() }}, you are executing a method rather than accessing a property in Angular. As a result, Angular will evaluate this expression each time it examines for changes, linking it with the DoCheck lifecycle hook and causing the console to log the value twice.

To remedy this issue, transform value into a property by implementing both a getter and setter, and make use of two-way data binding.

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