# Advanced: $THIS

{% hint style="info" %}
This documentation is unfinished
{% endhint %}

Advanced features such as [getting parameters from the URL bar](/features/what-are-nfts/advanced-url-query-params.md), or referencing the [current user](/features/what-are-nfts/advanced-usdcurrent_user.md) are important to building dynamic functionality for Collectibles. To complete this functionality and give users the ability to dynamically generate links from Collectibles in a list to a page of a single collectible, we have created the ability for an HTML block to dynamic reference itself with the const `$THIS...`

### Usage

The `$THIS...` const is useful when it is necessary to refer to the current item, for example when creating dynamic links that should be unique for each collectible item.  

| CONST                   | Purpose                                   |
| ----------------------- | ----------------------------------------- |
| `$THIS_ContractAddress` | Substituted with current Contract Address |
| `$THIS_TokenID`         | Substituted with current TokenID          |
| `$THIS_OwnerAddress`    | Substitutes with current OwnerAddress     |

### Example

For a live Demo: [DappHero-nft-example](https://glitch.com/~dapphero-nft-example).

Suppose you wanted to build a webpage that showed a dynamic list of Collectibles based on the contract address of a particular NFT contract. This is fairly easy to do, [ list the Collectibles](/features/what-are-nfts/listing-collectables.md#general-concepts). Now let's say you wrap each Token's image in an `anchor` tag, turning the image itself into a link that when clicked upon takes the user to a new webpage that shows a [Single Collectible](/features/what-are-nfts/single-collectibles.md). Creating a Single Collectible is also fairly easy, but the question is- how would you pass the data about WHICH collectible you want to display on the Single Collectible page? 

This is where we use `$THIS...`

```markup
<div
      data-dh-feature="nft"
      data-dh-property-tag-id="000"
      data-dh-property-asset-contract-address="<<contractAddress>>">
     
   <div
      data-dh-property-tag-id="000"
      data-dh-property-asset-item="true">
      <a
         href="./singleNFT.html?assetTokenId=$THIS_TokenID&assetContractAddress=$THIS_ContractAddress">
         <img data-dh-property-asset-json-path="image_url"/>
         </a>
     </div></div>
```

Let us take a closer look at line 9-12. What we are doing here is creating a link to a new page but passing URL Query Params for the DappHero engine to catch in the `singleNFT.html` page. You could manually pass the details `assetTokenId=1234` but then you would be stuck always rendering this one token. Instead, because we are inside the `asset container` from line 6-9 which gets rendered for each Collectible returned, we can access THIS specific token. If we use $THIS\_TokenID in the `href` link, it will get replaced with the token currently displayed, for example '1234'. If we do the same for the `assetContractAddress` we can now link to the `singleNFT.html` page passing all the information required for that page to render dynamically the specific collectible token we are interested in.&#x20;

```markup
<a
href="./singleNFT.html?assetTokenId=$THIS_TokenID&assetContractAddress=$THIS_ContractAddress">
<img data-dh-property-asset-json-path="image_url"/>
</a>
```

### Forms

Using the `$THIS...` const is useful for more than just creating dynamic links- it can also be used to create dynamic forms. This means you can combine the Collectible feature with other features like smart contracts- allowing users to interact with smart contracts using the about the current token they are looking for. A great example for this would be to create a Collectible store front connected to a smart contract to let people buy or sell Collectibles directly from your website!

Have a look at this simple example.&#x20;

```markup
<form action="">
        TokenID: <input type="text" value="$THIS_TokenID"><br><br>
        Owner Address: <input type="text" value="$THIS_OwnerAddress"><br><br>
        <input type="submit" value="Submit">
</form> 
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.dapphero.io/features/what-are-nfts/advanced-usdthis.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.