LangChain Fundamentals

Relax. We'll talk through this in plain words — no textbook voice.

What you'll walk away with

Understand LangChain Fundamentals without any of the intimidation
Get hands-on practice trying it yourself
Learn to spot — and smile past — the easy-to-make mistakes

Learn the basics of wiring up model, prompt, tool, and retrieval components with LangChain.

Let's think about it this way for a second

LangChain is a framework that connects model providers, prompts, tools, and retrieval for AI applications through a standard interface. You may not need it for a single, plain API call, but once your workflow gets more complex, it makes swapping and experimenting with components a lot easier.

LangChain Fundamentals lesson illustration — AI Applications — LangChain Fundamentals

Let's connect this to everyday life

You should be clear on why you're reaching for a framework in the first place. For a simple chat, the provider SDK alone is often smaller and simpler. Once retrieval, tools, and tracing come into the picture, LangChain's abstractions start to pay off.

Understand the model interface
Separate the prompt template from the data
Use structured output
Choose the SDK when you don't need the extra complexity

Let's try it hands-on together

javascript

import { ChatOpenAI } from "@langchain/openai";

const model = new ChatOpenAI({ model: "gpt-5.6" });
const response = await model.invoke(
  "RAG ကို မြန်မာလို စာကြောင်းသုံးကြောင်းဖြင့် ရှင်းပြပါ။",
);

console.log(response.content);

You should see

You'll get an AI response through the LangChain model interface.

5-minute try-it

Turn a prompt into a template with two variables. Compare the code complexity against a version that uses the provider SDK directly.

A quick word of caution

Don't treat AI output as the final word. Have a human review anything important — including code and user data — before it's actually used.

LangChain JavaScript overview — LangChain

Easy traps

Adding abstraction layers you don't actually need
Not checking the official docs when the framework version changes

Exercise

Turn a prompt into a template with two variables. Compare the code complexity against a version that uses the provider SDK directly.

You'll know it worked when: You'll get an AI response through the LangChain model interface.