sflwa

This plugin enhances Gravity Forms by providing the ability to export individual form entries as a <code>.json</code> file directly from the entries list. It allows you to define a custom JSON structure using a template editor within each form’s settings, where you can insert Gravity Forms merge tags and even utilize conditional logic shortcodes. A live preview feature helps you validate your JSON template before export.
<h3>Instructions</h3>
<ol>
<li>Activate the plugin.</li>
<li>Go to Forms > Forms, then select ‘Settings’ for the desired form.</li>
<li>Click on the ‘JSON Export’ tab.</li>
<li>Enable JSON Export Link: Check the box to display the “Download JSON Export” link on individual entry pages for this form.</li>
<li>Custom JSON Output Template: Enter your desired JSON structure in the textarea.
<ul>
<li>Use standard Gravity Forms merge tags (e.g., <code>{field_id}</code>, <code>{entry_id}</code>, <code>{date_created:format:Y-m-d}</code>).</li>
<li>Merge tags will be automatically formatted as <code>"key":"{merge_tag}"</code> when inserted from the dropdown.</li>
<li>You can also use Gravity Forms conditional shortcodes (e.g., <code>[gravityforms action='conditional' merge_tag='{Name (First):1.3}' condition='isnot' value='Philip']"custom_field":"conditional_value"[/gravityforms]</code>) to include dynamic content.</li>
</ul>
</li>
<li>Preview JSON Export: Click the ‘Preview JSON Export’ button to see a live preview of your generated JSON based on the latest entry for that form. This helps in validating your template.</li>
<li>Save Settings: Click ‘Save Settings’ to apply your changes.</li>
<li>To export an entry, go to Forms > Entries, hover over an entry, and click the ‘Download JSON Export’ link.</li>
</ol>

Custom JSON Export for Gravity Forms

A plugin to export individual Gravity Forms entries to a customizable JSON file.

svrooij

Since wordpress version 4.9.? wordpress includes the functionality provided by this plugin in the core of wordpress.
Checkout https://developer.wordpress.org/rest-api/using-the-rest-api/global-parameters/#_fields for functionality included in the wordpress core, 
they made it even better by filtering the amount of data pulled from the database.
This plugin will no longer be maintained since it has been superseded by the core functionality.
The <a href="https://wordpress.org/plugins/rest-api/" rel="ugc">wp-rest-api-v2</a> returns a lot of properties. 
It could be very useful (or mobile-data-friendly) to only return the properties needed by the application.
If you only want titles and links of some articles it doesn’t make sense to return the content or the excerpt.
This isn’t limited to posts, it also works on custom posttypes, categories, pages, terms, taxonomies and comments.
Instead of returning:
<pre><code>{
 "id": 2138,
 "date": "2015-10-25T15:31:03",
 "guid": {
 "rendered": "http://worldofict.nl/?p=2138"
 },
 "modified": "2015-10-25T15:31:03",
 "modified_gmt": "2015-10-25T14:31:03",
 "slug": "rechtenvrije-fotos",
 "type": "post",
 "link": "http://worldofict.nl/tip/2138-rechtenvrije-fotos/",
 "title": {
 "rendered": "Rechtenvrije foto’s"
 },
 "content": {
 "rendered": ".. A lot of content .. "
 },
 "excerpt": {
 "rendered": " .. A lot of content ..."
 },
 "author": 2,
 "featured_image": 2139,
 "comment_status": "open",
 "ping_status": "open",
 "sticky": false,
 "format": "standard",
 //.. even more tags ....
}
</code></pre>
It can return (with <code>fields=id,title.rendered,link</code> as GET parameter)
<pre><code>{
 "id": 2138,
 "link": "http://worldofict.nl/tip/2138-rechtenvrije-fotos/",
 "title": {
 "rendered": "Rechtenvrije foto’s"
 }
}
</code></pre>
<h4>Notes</h4>
<ol>
<li>If you specify fields so it wouldn’t return data the default response is send back to the client.</li>
<li>(for developers) something wrong with this plugin? <a href="https://github.com/svrooij/rest-api-filter-fields/" rel="nofollow ugc">Github</a></li>
<li>If you liked the plugin <a href="https://github.com/sponsors/svrooij" rel="nofollow ugc">consider sponsoring me</a></li>
</ol>

REST API – Filter Fields

This is hands-down the best REST API extension available.

Best REST API plugin

Filter the properties returned by the Wordpress rest api V2 (only needed until wordpress 4.9)

Custom JSON Export for Gravity Forms vs REST API – Filter Fields