---
id: import-external-libraries-using-runjs
title: Import External Libraries using RunJS
---
ToolJet allows you to integrate external JavaScript libraries into your application using RunJS queries. This guide walks you through the process of importing and utilizing these libraries effectively.
## Choosing Libraries
You can import various JavaScript libraries using their Content Delivery Network (CDN) links. Find the CDN links for your desired open-source projects on [jsDelivr](https://www.jsdelivr.com/).
## Creating a New App and RunJS Query
- Create a new app from the ToolJet Dashboard.
- Once the app is ready, choose ToolJet's deafult **JavaScript** Data Source from the query panel.
## Importing Libraries
Once the query is created, add the following code:
```js
// Function to add script dynamically
function addScript(src) {
return new Promise((resolve, reject) => {
const scriptTag = document.createElement('script');
scriptTag.setAttribute('src', src);
scriptTag.addEventListener('load', resolve);
scriptTag.addEventListener('error', reject);
document.body.appendChild(scriptTag);
});
}
try {
// Importing MathJS
await addScript('https://cdn.jsdelivr.net/npm/mathjs@11.7.0');
// Importing FlattenJS
await addScript('https://cdn.jsdelivr.net/npm/flattenjs@2.1.3/lib/flatten.min.js');
// Showing a success alert
await actions.showAlert("success", 'Mathjs and Flatten imported');
} catch (error) {
console.error(error);
}
```
After adding the code, click on the **Run** button in the query panel, an alert should pop up with the message "Mathjs and Flatten imported."
:::tip
Enable the **Run this query on application load?** option to make the libraries available throughout the application as soon as the app is loaded.
:::
## Examples
### 1. Flattening JSON Objects using FlattenJS
- Create a new *RunJS* query using the Flatten library (imported earlier) to flatten a JSON object.
- In the code section of the query, add the following code:
```js
return flatten({
key1: {
keyA: 'valueI'
},
key2: {
keyB: 'valueII'
},
key3: { a: { b: { c: 2 } } }
});
```
- Preview the output in the query manager or click **Run** in the query panel to see the flattened JSON.
### 2. Computation using MathJS
- Create another *RunJS* query utilizing the MathJS library for a calculation.
- In the code section of the query, add the following code:
```js
return math.atan2(3, -3) / math.pi;
```
- Preview the output in the query manager or click **Run** in the query panel to see the result of the calculation.
