How do I call an AI API from Node.js for text classification?

You can call an AI API from Node.js for text classification by sending the text you want classified to a model and asking it to return one of your labels.

Here’s a simple approach using Node.js and fetch.

1) Install Node.js

Make sure you have Node 18+ so fetch is available globally.

2) Example: classify text with an AI API

const apiKey = process.env.OPENAI_API_KEY;

async function classifyText(text) {
  const response = await fetch("https://api.openai.com/v1/responses", {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "Authorization": `Bearer ${apiKey}`,
    },
    body: JSON.stringify({
      model: "gpt-4.1-mini",
      input: [
        {
          role: "system",
          content: "You are a text classifier. Classify the user's text into one of: spam, urgent, normal. Reply with only the label."
        },
        {
          role: "user",
          content: text
        }
      ]
    }),
  });

  if (!response.ok) {
    throw new Error(`API error: ${response.status} ${await response.text()}`);
  }

  const data = await response.json();
  return data.output_text.trim();
}

(async () => {
  const label = await classifyText("Win a free iPhone now!!! Click here.");
  console.log(label);
})();

3) Set your API key

Set it in your environment:

export OPENAI_API_KEY="your_api_key_here"

On Windows PowerShell:

$env:OPENAI_API_KEY="your_api_key_here"

4) Notes for classification

For best results:

• Define a small fixed set of labels
• Tell the model to output only one label
• Provide examples if needed
• Validate the returned label in your code

5) Safer parsing example

If you want to make sure the output is one of the allowed labels:

const allowed = new Set(["spam", "urgent", "normal"]);
const label = (await classifyText(text)).toLowerCase();

if (!allowed.has(label)) {
  throw new Error(`Unexpected label: ${label}`);
}

6) Using the official SDK

If you prefer the OpenAI SDK:

npm install openai

import OpenAI from "openai";

const client = new OpenAI({ apiKey: process.env.OPENAI_API_KEY });

async function classifyText(text) {
  const response = await client.responses.create({
    model: "gpt-4.1-mini",
    input: [
      {
        role: "system",
        content: "Classify the text into one of: spam, urgent, normal. Reply with only the label."
      },
      {
        role: "user",
        content: text
      }
    ]
  });

  return response.output_text.trim();
}

If you want, I can also show:

• how to do this with structured JSON output
• how to classify into multiple categories
• how to use Express.js to expose a classification endpoint