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How to detect the changement of a variable in javascript?

Is there any idea on how to trigger / detect a changement on a javascript variable ?
the mail goal is to show on every change , the new value of the variable in a span .

I searched on the internet but I found that there is no event or Eventlistner that works with variable

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2

Answers


  1. 0 
    Object.defineProperty(globalThis, 'some_value', {
  set(value) {
    console.log('some_value set to: ', value)
  }
});

some_value = 3

//some_value set to:  3

some_value = 2

//some_value set to:  2

    Granted this works if your variable in global.

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  2. 0

    You may utilize this vanilla JS solution that @twalow has suggested.

    But if you want to dive deeper into reactive programming try this stackblitz out

    The snippets:

    TS:

    // Import stylesheets
import { interval, startWith, Subject, tap } from 'rxjs';
import './style.css';

// Write TypeScript code!
const appDiv: HTMLElement = document.getElementById('app');

const subject = new Subject();

subject
  .pipe(
    tap((value) => {
      appDiv.innerHTML = `<h1>TypeScript Starter ${value}</h1>`;
    })
  )
  .subscribe();

/**
 * pretending subject value changes
 */
interval(2000)
  .pipe(
    startWith(-1),
    tap(console.log),
    tap((value) => subject.next(value))
  )
  .subscribe();

    HTML:

    <div id="app"></div>
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