> ## Documentation Index
> Fetch the complete documentation index at: https://docs.invoca.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Dynamic Number Replacement Exhibiting a Flicker When Number Swapping

> A brief flicker of the original phone number before it swaps is caused by the Invoca Tag's asynchronous loading — hide it with custom code that reveals the number only once swapping completes.

## Symptoms

When a webpage loads, the hardcoded site phone number briefly appears before Dynamic Number Insertion swaps it with an Invoca number, creating a flickering effect.

**Applies to:** Accounts using the Invoca Tag for Dynamic Number Insertion on their webpages.

## Cause

Number flicker can be caused by the asynchronous loading of the Invoca Tag JavaScript on a site. JavaScript commands run one after another, and the Invoca Tag is set to run after the commands that load the phone number onto the page.

## Resolution

*This solution requires development on the customer's part, within their own codebase.*

1. If you're using an Invoca `numberSelector`, target that CSS selector in the next step. Otherwise, create a new CSS class for phone numbers on your page — the example below uses `.InvocaNumber`.
2. Insert the following code in the custom code block of your Invoca Tag Wizard:

```js theme={null}
function showNumber(){
  var elements = document.querySelectorAll(".InvocaNumber");
  elements.forEach(function (el) {
    el.style.opacity = 1;
  })
  // or this code if your site uses JQuery.
  $(".InvocaNumber").animate({'opacity': 1}, 250);
};

options.onComplete = showNumber;

setTimeout(function(){
  showNumber();
}, 3000);

return options;
```

* `onComplete`: covers the normal case — showing the number by updating its style as soon as the tag returns with a DNI number and swaps it in.
* `setTimeout`: a fallback for cases where the tag doesn't run, or there's an error reaching the Invoca server (so `onComplete` never fires) — this ensures the container showing the number still displays the original number.

## Where to go next

* [Tag Wizard: Custom Code](/s/article/tag-wizard-custom-code)
* [Tag Wizard: Custom Code Settings](/s/article/tag-wizard-custom-code-settings)