trying to datalayer update with set() build-in method but not updating

trying to update a value in my datalayer but I can't get it to work. See code below. This inside a class that has btn click methods. btw.

if (window.google_tag_manager["GTM-XXXXX"].dataLayer.get('ecommerce') !== undefined) {
      console.log('update')
      window.google_tag_manager["GTM-XXXXXX"].dataLayer.set('ecommerce', {
        'productId': `${this.product.id}`, 
        'productName': `${this.product.productName}`
      })
   
    } else {
      console.log('create')
      window.dataLayer.push({ 
        'ecommerce': {
          'productId': `${this.product.id}`, 
          'productName': `${this.product.productName}`
      }});
    }

According to this documentation, it should work. https://javascript.tutorialink.com/how-to-update-a-datalayer-variable/

The values get picked up upon click.

Not sure why you need to update the dataLayer

You can just push it and it will update automatically if you use Google Tag Manager - DataLayer Variable to get the data.

Any specific use case or requirement?