Fill Browser Form

Overview

This skill is designed to assist users in automating the process of filling out web forms directly in their browsers. By following a structured approach, it enables the generation of JavaScript code that can be executed in the browser's console to populate form fields fast and accurately.

When to Use This Skill

Use this Skill when a user needs to fill form fields in their browser

Workflow

Step 1: Extract HTML from the page

When the user asks to fill a form, you respond immediately with these instructions to obtain the HTML of the page: Ask the user to open DevTools (F12) in their browser and run the following command in the console to copy the page HTML to their clipboard:

{
  const textarea = document.createElement("textarea");
  textarea.value = document.body.outerHTML;
  document.body.appendChild(textarea);
  textarea.select();
  document.execCommand("copy");
  document.body.removeChild(textarea);
  ("pagina gekopieerd naar klembord");
}

Just show this code snippet in a code block inline, do not use an artifact for this step.

Ask the user to paste the result back to you.

Step 2: Analyze the HTML Structure

When the user provides the HTML, analyze the form fields in the HTML and understand:

• How fields are labeled and structured
• How to add new rows/sections/instances if needed
• The DOM structure how to navigate from a label to the accompanying input element

Step 3: Generate the Form-Filling Script

Create a script that follows these important rules:

Timing Requirements

• Wait 200ms between filling different fields
• Wait 500ms after actions that modify the page (e.g., adding new rows/sections/fields, opening/closing panels)

Field Filling Process

For each field, perform these actions:

1. Focus the field (this scrolls it into view)
2. Set the value or checked attribute
3. Fire a synthetic change or input event

Element Selection Strategy

Always find the correct element using this approach:

• Search for the element based on its associated text label
• Take the last element on the page with that text label
• Navigate to the appropriate ancestor element
• Use querySelector from there to find the correct input element
• Use helper functions specific to the HTML structure

Helper Function Examples

// Finds the last input element with an associated label element on the page
function findInputElementByLabel(labelText) {
  const labels = Array.from(document.querySelectorAll("label"));
  const matchingLabel = labels.findLast((label) =>
    label.textContent.includes(labelText)
  );

  if (matchingLabel) {
    if (matchingLabel.htmlFor) {
      return document.getElementById(matchingLabel.htmlFor);
    }
    const nestedInput = matchingLabel.querySelector("input,select,textarea");
    if (nestedInput) {
      return nestedInput;
    }
  }
  throw new Error("Field not found for label: " + labelText);
}

// Finds the input element associated with the last  containing labelText
function findInputElementByDivLabel(labelText) {
  const label = Array.from(document.querySelectorAll("div.label")).findLast(
    (el) => el.textContent.includes(labelText)
  );

  if (!label) {
    throw new Error("Label not found: " + labelText);
  }

  // Navigate to the container parent
  const fieldContainer = label.closest("div.container");

  const input = fieldContainer.querySelector("custom-text-input input");
  if (!input) {
    throw new Error("Input not found for label: " + labelText);
  }

  return input;
}

Step 4: Script Format

Create a simple, compact script with:

• Each declaration and function documented with one line of comment in language the user uses.
• Wrapped in an IIFE (Immediately Invoked Function Expression)
• Proper error handling and logging to the console

Step 5: Delivery Instructions

Provide the script as an artifact and instruct the user to:

1. Run the script in the DevTools console
2. If something goes wrong, respond with the console output or a description of what failed

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: johan-gorter
• Source: johan-gorter/fill-browser-form
• License: MIT

Install and usage instructions live in the source repository linked above.