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Custom Langchain Agent Written In Javascript

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A recipe for Custom Langchain Agent Written In Javascript

Recipe Template

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    "meta": {
        "instanceId": "021d3c82ba2d3bc090cbf4fc81c9312668bcc34297e022bb3438c5c88a43a5ff"
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    "name": "LangChain - Example - Code Node Example",
    "tags": [
        {
            "id": "snf16n0p2UrGP838",
            "name": "LangChain - Example",
            "createdAt": "2023-09-25T16:21:55.962Z",
            "updatedAt": "2023-09-25T16:21:55.962Z"
        }
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    "nodes": [
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            "position": [
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            ],
            "parameters": {
                "options": []
            },
            "credentials": {
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                    "id": "4jRB4A20cPycBqP5",
                    "name": "OpenAI account - n8n"
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            },
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            "position": [
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            "parameters": {
                "width": 432,
                "height": 237,
                "content": "## Self-coded LLM Chain Node"
            },
            "typeVersion": 1
        },
        {
            "id": "05ad7d68-5dc8-42f2-8274-fcb5bdeb68cb",
            "name": "When clicking \"Execute Workflow\"",
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            "name": "Set",
            "type": "n8n-nodes-base.set",
            "position": [
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            ],
            "parameters": {
                "values": {
                    "string": [
                        {
                            "name": "input",
                            "value": "Tell me a joke"
                        }
                    ]
                },
                "options": []
            },
            "typeVersion": 2
        },
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            "parameters": {
                "values": {
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                        {
                            "name": "input",
                            "value": "What year was Einstein born?"
                        }
                    ]
                },
                "options": []
            },
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                    "name": "OpenAI account - n8n"
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                "content": "## Self-coded Tool Node"
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            "name": "Custom - Wikipedia",
            "type": "@n8n\/n8n-nodes-langchain.code",
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            "parameters": {
                "code": {
                    "supplyData": {
                        "code": "console.log('Custom Wikipedia Node runs');\nconst { WikipediaQueryRun } = require('langchain\/tools');\nreturn new WikipediaQueryRun();"
                    }
                },
                "outputs": {
                    "output": [
                        {
                            "type": "ai_tool"
                        }
                    ]
                }
            },
            "typeVersion": 1
        },
        {
            "id": "9c729e9a-f173-430c-8bcd-74101b614891",
            "name": "Custom - LLM Chain Node",
            "type": "@n8n\/n8n-nodes-langchain.code",
            "position": [
                880,
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            ],
            "parameters": {
                "code": {
                    "execute": {
                        "code": "const { PromptTemplate } = require('langchain\/prompts');\n\nconst query = $input.item.json.input;\nconst prompt = PromptTemplate.fromTemplate(query);\nconst llm = await this.getInputConnectionData('ai_languageModel', 0);\nlet chain = prompt.pipe(llm);\nconst output = await chain.invoke();\nreturn [ {json: { output } } ];"
                    }
                },
                "inputs": {
                    "input": [
                        {
                            "type": "main"
                        },
                        {
                            "type": "ai_languageModel",
                            "required": true,
                            "maxConnections": 1
                        }
                    ]
                },
                "outputs": {
                    "output": [
                        {
                            "type": "main"
                        }
                    ]
                }
            },
            "typeVersion": 1
        },
        {
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            "name": "Agent",
            "type": "@n8n\/n8n-nodes-langchain.agent",
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                        "type": "main",
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            ]
        },
        "Set1": {
            "main": [
                [
                    {
                        "node": "Agent",
                        "type": "main",
                        "index": 0
                    }
                ]
            ]
        },
        "OpenAI": {
            "ai_languageModel": [
                [
                    {
                        "node": "Custom - LLM Chain Node",
                        "type": "ai_languageModel",
                        "index": 0
                    }
                ]
            ]
        },
        "Chat OpenAI": {
            "ai_languageModel": [
                [
                    {
                        "node": "Agent",
                        "type": "ai_languageModel",
                        "index": 0
                    }
                ]
            ]
        },
        "Custom - Wikipedia": {
            "ai_tool": [
                [
                    {
                        "node": "Agent",
                        "type": "ai_tool",
                        "index": 0
                    }
                ]
            ]
        },
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How to Use an n8n Template

1

Create a New Workflow

Click "New Workflow" in your n8n dashboard to get started.

2

Copy & Paste Template

First, copy this template: Click here to copy the JSON .
Then, in n8n, click the three dots (···) → "Import from file" and paste the JSON code.

3

Customize the Nodes

Go through each node in the workflow to update inputs like spreadsheet IDs, email addresses, or message content. Adjust field mappings to match your data.

4

Grant Access

For nodes that connect to external apps (like Google Sheets or Slack), you'll need to grant access. Connect your accounts using OAuth or an API key and save the credentials in the node.

5

Test It

Run the workflow by clicking "Execute Node" for each step or "Run Once" for the whole thing. Check the right sidebar to inspect data and debug any errors (they'll show up in red).

6

Activate Workflow

Once everything works as expected, click the "Activate" toggle to turn your workflow on. You're all set!

Frequently Asked Questions

How long does it take to implement this development recipe?

This recipe typically takes 30 minutes to implement, depending on your experience level with the tools involved.

What tools do I need for this recipe?

You'll need: n8n. All tools are linked above with setup instructions.

Is this recipe free to use?

This recipe uses a mix of free and paid tools. Check individual tool pricing above.

Do I need coding experience for this recipe?

Most tools in this recipe are no-code or low-code solutions, making them accessible to beginners. Each tool includes difficulty level indicators.

Can I customize this recipe?

Absolutely! This recipe provides a foundation that you can adapt to your specific needs. Feel free to add or remove tools based on your requirements.

What if I get stuck implementing this recipe?

Each tool includes documentation links and support resources. You can also reach out to our community or consider hiring one of our verified agencies for assistance.