Evaluate JavaScript Node

Browser Node - Advanced

Execute custom JavaScript code in the browser context

Overview

The Evaluate JavaScript node allows you to run custom JavaScript code directly in the web page's browser context. This gives you full access to the page's DOM, JavaScript variables, and APIs for complex operations that aren't covered by other nodes.

Advanced Node

This is an advanced node that requires JavaScript knowledge. Prefer built-in nodes when possible for better maintainability and error handling.

Parameters

Configuration options for this node

code

JavaScript

Required

JavaScript code to run in the page. The node wraps your code in a function, so top-level `return` is allowed.

Example: return document.title;

targetVar

String

Workflow variable name to store the returned value under. Reference it later with {{yourVarName}} in any downstream node.

Example: pageTitle, productList

Usage Examples

Example 1: Get Page Data

Extract complex data from the page

// Extract all product info from a listing
return Array.from(document.querySelectorAll('.product')).map(el => ({
  name: el.querySelector('.name')?.textContent,
  price: el.querySelector('.price')?.textContent,
  url: el.querySelector('a')?.href
}));

Example 2: Modify Page State

Change page content or trigger JavaScript functions

// Close all modal dialogs
document.querySelectorAll('.modal.open').forEach(modal => {
  modal.classList.remove('open');
});
return 'Closed all modals';

Example 3: Call Page Functions

Invoke existing JavaScript functions on the page

// Call a React app's state update function
if (typeof window.updateCart === 'function') {
  window.updateCart({ quantity: 5 });
  return true;
}
return false;

Example 4: Wait for Condition

Create custom wait logic

// Wait for a React app to finish loading
return new Promise((resolve) => {
  const checkLoaded = () => {
    if (document.querySelector('[data-loaded="true"]')) {
      resolve(true);
    } else {
      setTimeout(checkLoaded, 100);
    }
  };
  checkLoaded();
});

Example 5: Interact with localStorage

Read or write to browser storage

// Get user preferences from localStorage
return JSON.parse(localStorage.getItem('userPrefs') || '{}');

Storing & Using the Result

Set Target Variable to capture whatever your script returns. The value then becomes available to every node after this one as {{yourVarName}}(simple substitution) or as {{$('Node Label').item.json.result}}(expression form that looks the value up by the node's label).

// Script — Target Variable: pageInfo
return JSON.stringify({
  title: document.title,
  inputCount: document.querySelectorAll('input').length,
  url: location.href
});

In a downstream Display Message node you'd then write:

Page data: {{pageInfo}}

Tip: if you return a deeply-nested object, prefer JSON.stringify(...). Execution history storage has a nested-object depth limit, and stringifying sidesteps it.

Return Values

Serializable Returns Only

Return values must be JSON-serializable. You can return:

Strings, numbers, booleans, null
Arrays and plain objects
Promises (will be awaited)

You cannot return DOM elements, functions, or circular objects.

Best Practices

Prefer Built-in Nodes

Before using Evaluate JavaScript, check if a built-in node can do what you need. Built-in nodes have better error handling and are easier to maintain.

Handle Errors

Wrap your code in try-catch blocks and return meaningful error messages. Uncaught errors will fail the workflow with potentially cryptic messages.

Keep Scripts Simple

Large, complex scripts are hard to debug. Break complex operations into multiple smaller Evaluate JavaScript nodes or combine with other node types.

Security Warning

Never execute untrusted user input as JavaScript. Always validate and sanitize any data used in scripts.

Evaluate JavaScript Node

Browser Node - Advanced

Execute custom JavaScript code in the browser context

Overview

Advanced Node

This is an advanced node that requires JavaScript knowledge. Prefer built-in nodes when possible for better maintainability and error handling.

Parameters

Configuration options for this node

code

JavaScript

Required

JavaScript code to run in the page. The node wraps your code in a function, so top-level `return` is allowed.

Example: return document.title;

targetVar

String

Workflow variable name to store the returned value under. Reference it later with {{yourVarName}} in any downstream node.

Example: pageTitle, productList

Usage Examples

Example 1: Get Page Data

Extract complex data from the page

// Extract all product info from a listing
return Array.from(document.querySelectorAll('.product')).map(el => ({
  name: el.querySelector('.name')?.textContent,
  price: el.querySelector('.price')?.textContent,
  url: el.querySelector('a')?.href
}));

Example 2: Modify Page State

Change page content or trigger JavaScript functions

// Close all modal dialogs
document.querySelectorAll('.modal.open').forEach(modal => {
  modal.classList.remove('open');
});
return 'Closed all modals';

Example 3: Call Page Functions

Invoke existing JavaScript functions on the page

// Call a React app's state update function
if (typeof window.updateCart === 'function') {
  window.updateCart({ quantity: 5 });
  return true;
}
return false;

Example 4: Wait for Condition

Create custom wait logic

// Wait for a React app to finish loading
return new Promise((resolve) => {
  const checkLoaded = () => {
    if (document.querySelector('[data-loaded="true"]')) {
      resolve(true);
    } else {
      setTimeout(checkLoaded, 100);
    }
  };
  checkLoaded();
});

Example 5: Interact with localStorage

Read or write to browser storage

// Get user preferences from localStorage
return JSON.parse(localStorage.getItem('userPrefs') || '{}');

Storing & Using the Result

// Script — Target Variable: pageInfo
return JSON.stringify({
  title: document.title,
  inputCount: document.querySelectorAll('input').length,
  url: location.href
});

In a downstream Display Message node you'd then write:

Page data: {{pageInfo}}

Tip: if you return a deeply-nested object, prefer JSON.stringify(...). Execution history storage has a nested-object depth limit, and stringifying sidesteps it.

Return Values

Serializable Returns Only

Return values must be JSON-serializable. You can return:

Strings, numbers, booleans, null
Arrays and plain objects
Promises (will be awaited)

You cannot return DOM elements, functions, or circular objects.

Best Practices

Prefer Built-in Nodes

Before using Evaluate JavaScript, check if a built-in node can do what you need. Built-in nodes have better error handling and are easier to maintain.

Handle Errors

Wrap your code in try-catch blocks and return meaningful error messages. Uncaught errors will fail the workflow with potentially cryptic messages.

Keep Scripts Simple

Large, complex scripts are hard to debug. Break complex operations into multiple smaller Evaluate JavaScript nodes or combine with other node types.

Security Warning

Never execute untrusted user input as JavaScript. Always validate and sanitize any data used in scripts.

Evaluate JavaScript Node

Overview

Advanced Node

Usage Examples

Storing & Using the Result

Return Values

Serializable Returns Only

Best Practices

Prefer Built-in Nodes

Handle Errors

Keep Scripts Simple

Security Warning

Related Documentation

Wait for Function

Extract Text Node

Variables Guide

Evaluate JavaScript Node

Overview

Advanced Node

Usage Examples

Storing & Using the Result

Return Values

Serializable Returns Only

Best Practices

Prefer Built-in Nodes

Handle Errors

Keep Scripts Simple

Security Warning

Related Documentation

Wait for Function

Extract Text Node

Variables Guide