Glitchy Devs Build-Your-Own Frontend Framework

Last updated: 27 July 2026

Apply a layered, from-scratch methodology to design and build a custom frontend framework with templating, virtual DOM, and reactive state management in pure JavaScript.

// TL;DR

The Glitchy Devs Build-Your-Own Frontend Framework is a layered, from-scratch methodology for building a custom JavaScript frontend framework with templating, a virtual DOM, and reactive state management. You use tagged template literals as a template engine, Snabbdom for VDOM diffing, and pure state mutation functions wrapped into 'mapped methods' for automatic reactivity. Use it when you want to deeply understand how React, Vue, or Angular work under the hood, or when you need a lightweight custom framework without black-box abstractions. A component is always a combination of a template function, a methods object, and an initial state.

Framework

// When should you build your own frontend framework from scratch?

Use this skill when you want to deeply understand how frameworks like React, Vue, or Angular work under the hood, or when you want to build a lightweight custom frontend framework for a project without relying on black-box abstractions.

// What do you need before building your custom framework?

Project directory / reporequired
A fresh or existing JavaScript project with Node.js available, ideally scaffolded with Parcel as the bundler
Target UI componentrequired
A description of the component you want to build (e.g. a user card, a to-do item) to drive the implementation
Initial state shaperequired
The data your component needs to display (e.g. firstName, lastName, todoList)
Desired interactions
The user events you need to handle (e.g. click to change name, submit to add item)

// What core principles guide this from-scratch framework methodology?

No Black Boxes

Every part of the framework — templating, virtual DOM, state management — must be explicable and hand-built. If you cannot create it, you do not understand it.

Tag Template Literal as Template Engine

Instead of JSX or external templating languages, use JavaScript's tagged template literals to parse static strings and dynamic values, combining them into HTML structures without additional libraries.

Virtual DOM Abstraction

Never manipulate the real DOM directly. All changes flow through a Virtual DOM (VDOM) first; the library (Snabbdom) diffs old and new VDOMs and patches only what has changed.

State Mutation Functions

State is never mutated in place. State mutation functions take the current state plus parameters and return a new state object using the spread operator, keeping transformations predictable and traceable.

Mapped Methods for Reactivity

Each method in the methods object is wrapped by the framework into a 'mapped method' that automatically updates state, re-evaluates the template, and patches the DOM — achieving reactivity without manual wiring.

createElement as a Higher-Order Function

createElement(tagName) returns a function that processes tagged template literals, producing a virtual node object containing both the element type and its rendered template. This enables lazy, declarative element definitions.

Component = Template + Methods + Initial State

A component in this framework is always a combination of three things: a template function (the HTML structure), a methods object (state mutations), and an initial state object (default data). These are passed to createComponent to produce a reusable unit.

// How do you build a frontend framework from scratch step by step?

1
Scaffold the project with Parcel and install Snabbdom
Use Parcel as a zero-configuration bundler (no webpack config needed). Install Snabbdom via yarn: `yarn add snabbdom`. Configure Babel with the env preset to transpile modern JavaScript. Create directories: `framework/` for core logic and `source/` for application components.
2
Build the createElement function using tagged template literals
In `framework/element.js`, define `createElement(tagName)` as a higher-order function. It returns a function that accepts `(strings, ...args)` — the tagged template literal signature. Use `reduce` on the strings array to interleave static strings and dynamic arg values into a single HTML string. The returned object must expose both `type` (the tag name) and `template` (the combined string). Export specific element helpers like `div` and `p` by calling `createElement('div')` etc. Avoid code duplication — never write separate reducers per element.
3
Refactor createElement to produce Snabbdom virtual nodes (h function)
Import Snabbdom's `h` (hyperscript) function. Update `createElement` so that instead of returning a plain string, it calls `h(tagName, data, children)` to create a virtual node. Introduce a `createReducer` helper that splits the reduce logic: if a dynamic arg is an event handler object (from the `on` module), accumulate it into an `on` object; otherwise concatenate it as a string. Pass the assembled `on` object as the data argument to `h`.
4
Build the init function to patch the real DOM using Snabbdom
In `framework/index.js`, initialise Snabbdom with `snabbdom.init([])` (add the eventlisteners module when events are needed). The `init(selector, component)` function selects the real DOM element via the CSS selector, then calls `patch(appElement, component.template)` to replace it with the virtual node. At this stage the app renders once — reactivity comes later.
5
Add event handling via Snabbdom's eventlisteners module
In `framework/event.js`, create event factory functions, e.g. `onClick(fn)` returns `{ click: fn }`. Include Snabbdom's eventlisteners module in `snabbdom.init([eventListenersModule])`. In `createElement`, when a dynamic arg is an event object (detected by checking its keys against known event names), route it to the `on` property of the `h` data argument rather than concatenating it as a string.
6
Define the initial state and state mutation functions
In your component file (e.g. `source/user.js`), define `initialState` as a plain object with default values. Define each mutation as a pure function: `(state, ...params) => ({ ...state, changedKey: newValue })`. Group all mutations into a `methods` object. Never mutate the state object directly — always return a new object using the spread operator.
7
Implement createComponent with mapped methods for reactivity
In `framework/index.js`, build `createComponent({ template, methods, initialState })`. This returns a render function. Inside, maintain a mutable `state` variable (set to `initialState`) and a `previous` variable (the last rendered VDOM). Build `mappedMethods` by iterating over `Object.keys(methods)` with `reduce`: each mapped method calls the original mutation to get new state, re-evaluates the template with updated state, and calls `patch(previous, nextNode)` to update only changed DOM parts, then stores `nextNode` as the new `previous`. The initial render calls `template(props, state, mappedMethods)` and returns the VDOM ready for the first `patch`.
8
Author a real-world component using the framework
In `source/user.js` (or your own component file), import `div` from `framework/element.js`, `onClick` from `framework/event.js`, and `createComponent` from `framework/index.js`. Define `initialState`, `methods`, and a `template` function that uses `div` with tagged template literals and attaches `onClick` handlers. Export the result of `createComponent({ template, methods, initialState })`. Keep template, methods, and state co-located in one file per component.
9
Wire the component into the app entry point and run
In `index.js`, import your component and call `init('#app', userComponent(props))`. Ensure `index.html` has a `<div id='app'></div>`. Run `yarn start` (which clears cache and launches Parcel dev server). Open `localhost:1234`. Confirm the component renders, click events fire, and DOM updates are scoped only to changed nodes.
10
Plan extensions: children rendering, lifecycle hooks, performance, style encapsulation, dependency injection
Children re-rendering: modify `createComponent` to accept and render child components as props. Lifecycle hooks: introduce `onMount`, `onUpdate`, `onUnmount` callbacks triggered at appropriate points in the render cycle. Performance: consider memoisation, batched updates (group multiple state mutations into one patch cycle), and virtual scrolling for long lists. Style encapsulation: use Shadow DOM API or CSS-in-JS to prevent style leakage. Dependency injection: pass services into components at creation time via a context or service-locator pattern rather than hardcoding them.

// What are real examples of components built with this framework?

A developer wants to build a reusable 'Profile Card' component that displays a user's name and job title, and lets a button click update the job title.

Define `initialState = { name: 'Alex', jobTitle: 'Engineer' }`. Write a mutation `changeTitle: (state, newTitle) => ({ ...state, jobTitle: newTitle })` inside `methods`. In the `template` function, use the `div` tagged template literal to render the name and job title, attaching an `onClick` that calls the mapped `changeTitle` method with a new value. Pass everything to `createComponent`. The mapped method handles state update, VDOM re-evaluation, and DOM patching automatically — the button click triggers an instant, scoped DOM update.

A developer needs a minimal counter widget — increment and decrement buttons update a displayed count.

Set `initialState = { count: 0 }`. Define `methods = { increment: (state) => ({ ...state, count: state.count + 1 }), decrement: (state) => ({ ...state, count: state.count - 1 }) }`. The template renders the count value and two buttons each wired with `onClick` to their respective mapped methods. Snabbdom patches only the text node holding the count on each click, leaving the rest of the DOM untouched.

// What mistakes should you avoid when building your own framework?

Skipping the createReducer refactor and writing inline reduce logic directly in createElement makes event handling impossible to add cleanly later.
Mutating the state object in place (e.g. `state.firstName = 'Thomas'`) instead of returning a new object with the spread operator breaks the predictability of state transformations.
Forgetting to include Snabbdom's eventlisteners module in `snabbdom.init([eventListenersModule])` means click handlers silently do nothing.
Patching a real DOM element (like `document.querySelector('#app')`) directly as the first argument to `patch` only works once — subsequent patches must use the previous virtual node stored in `previous`, not the real DOM element.
Not storing the last rendered VDOM in the `previous` variable means Snabbdom cannot diff correctly, causing full re-renders or errors.
Writing per-element reducer logic (separate functions for div, p, span, etc.) instead of using the `createElement` higher-order function leads to code duplication the methodology explicitly rejects.
Using the framework without at least basic JavaScript knowledge (template literals, destructuring, spread operator, reduce) will make the codebase opaque — the creator explicitly warns against this.

// What key terms should you know for this framework methodology?

Tag Template Literal: A JavaScript tagged template literal where a function (the 'tag') receives the static strings array and dynamic args array separately, enabling custom processing of the template — used here as the framework's template engine.
createElement: A higher-order function that takes a tag name and returns a tagged-template-literal handler. The handler combines static strings and dynamic values (including event objects) into a Snabbdom virtual node.
Virtual DOM (VDOM): A lightweight in-memory representation of the real DOM. The framework (via Snabbdom) diffs the old VDOM against a newly computed VDOM and patches only the changed nodes in the real DOM.
Snabbdom: The virtual DOM library used in this framework (the same one Vue.js forks). It provides the `h` (hyperscript) function to create virtual nodes and the `patch` function to efficiently update the real DOM.
h function (hyperscript): Snabbdom's function for creating virtual nodes: `h(tagName, data, children)`. It replaces direct DOM node creation and is the output of the refactored `createElement`.
patch: Snabbdom's core DOM-update function. It compares the previous virtual node with the next virtual node and applies the minimal set of real DOM changes needed.
State Mutation Function: A pure function with the signature `(state, ...params) => newState` that takes the current state and returns a new state object using the spread operator. Never mutates state in place.
Methods object: A plain object grouping all state mutation functions for a component. Passed to `createComponent`, where each entry is wrapped into a mapped method.
Mapped Methods: Wrapper functions generated by `createComponent` for each entry in the methods object. When called, a mapped method updates state, re-evaluates the template, and triggers a Snabbdom patch — implementing reactivity automatically.
createComponent: The core framework factory function. Accepts `{ template, methods, initialState }` and returns a render function. Internally manages state, previous VDOM, and mapped methods to make the component reactive.
Initial State: A plain JavaScript object defining the default values for a component's data. Set once at component creation; all subsequent state changes flow through mutation functions.
Change Deduction: The process by which the framework detects what has changed in state, recomputes the VDOM, and updates only the necessary parts of the real DOM — equivalent to React's reconciliation or Vue's reactivity system.
Parcel: The zero-configuration web application bundler used to serve and build the framework project. Requires no webpack-style config files.
createReducer: A helper function extracted from `createElement` that handles the reduce logic over template literal parts: concatenating strings for HTML content and collecting event handler objects into the `on` map.

// FREQUENTLY ASKED QUESTIONS

What is the Glitchy Devs build-your-own frontend framework method?

It's a from-scratch methodology for building a custom JavaScript frontend framework using three hand-built layers: templating with tagged template literals, a virtual DOM powered by Snabbdom, and reactive state management via mapped methods. Every part is explicable and hand-built — no black boxes. A component is always a template function, a methods object, and an initial state passed to createComponent.

What is a virtual DOM and why does this framework use one?

A virtual DOM (VDOM) is a lightweight in-memory representation of the real DOM. This framework never manipulates the real DOM directly — instead, all changes flow through the VDOM, and Snabbdom diffs the old and new VDOMs to patch only what changed. This makes DOM updates efficient and scoped, updating just the changed text node or element rather than re-rendering everything.

How do I build a template engine without JSX?

Use JavaScript's tagged template literals. Define createElement(tagName) as a higher-order function that returns a handler accepting (strings, ...args) — the tagged template signature. Inside, use reduce to interleave static strings and dynamic values into a Snabbdom virtual node via the h function. This gives you declarative HTML structures in pure JavaScript with zero external templating libraries or JSX transpilation.

How do I make state changes reactive in a custom framework?

Wrap each method in the methods object into a 'mapped method' inside createComponent. When called, the mapped method runs the pure state mutation to get new state, re-evaluates the template with that state, and calls Snabbdom's patch(previous, nextNode) to update only changed DOM nodes, then stores nextNode as the new previous. This achieves reactivity without manual DOM wiring.

How does building your own framework compare to just using React?

Building your own framework teaches you the mechanics React hides — reconciliation, reactivity, and templating become transparent rather than magic. React is production-hardened with a massive ecosystem; a hand-built framework is lightweight and fully understood but lacks community support, tooling, and edge-case coverage. Use the from-scratch approach for learning or minimal projects, and React for production apps needing scale and stability.

When should I build my own frontend framework instead of using an existing one?

Build your own when you want to deeply understand how frameworks work under the hood, or when a project needs a lightweight solution without heavy abstractions. Avoid it for large production apps where React, Vue, or Angular's ecosystem, tooling, and battle-tested reliability matter more. The methodology explicitly targets learning and minimal custom use cases, not enterprise-scale replacement.

What is Snabbdom and why is it used here?

Snabbdom is the virtual DOM library this framework uses — the same one Vue.js forks. It provides the h (hyperscript) function to create virtual nodes and the patch function to efficiently update the real DOM by diffing old and new VDOMs. Using Snabbdom lets you focus on framework design (templating, reactivity) instead of reimplementing DOM diffing from scratch.

What results can I expect after building this framework?

You'll have a working reactive component that renders once, handles click and submit events, and patches only changed DOM nodes on state updates. More importantly, you'll understand reconciliation, reactivity, and templating from first principles — demystifying React and Vue. You'll also gain a reusable createComponent factory you can extend with lifecycle hooks, children rendering, and performance optimizations.

What are mapped methods in this framework?

Mapped methods are wrapper functions that createComponent generates for each entry in your methods object. When you call a mapped method, it automatically updates state using your pure mutation function, re-evaluates the template with the new state, and triggers a Snabbdom patch to update the DOM. This is the mechanism that delivers automatic reactivity without you manually wiring DOM updates.

How do I handle click events in a from-scratch framework?

Create event factory functions in framework/event.js, like onClick(fn) returning { click: fn }. Include Snabbdom's eventlisteners module in snabbdom.init([eventListenersModule]). In createElement, detect when a dynamic arg is an event object and route it to the on property of the h data argument instead of concatenating it as a string. Forgetting the eventlisteners module makes handlers silently do nothing.

Do I need to know JavaScript before building my own framework?

Yes — at minimum you need template literals, destructuring, the spread operator, and reduce. The creator explicitly warns that without this foundation the codebase becomes opaque. The framework's core patterns — higher-order functions, tagged template literals, and pure state mutations returning new objects — all rely on solid intermediate JavaScript knowledge to be understandable and maintainable.

What is a state mutation function and why can't I mutate state directly?

A state mutation function is a pure function with signature (state, ...params) => newState that returns a new state object using the spread operator instead of changing the original. Mutating state in place (like state.firstName = 'Thomas') breaks predictability and traceability, and prevents the framework from reliably detecting changes and diffing VDOMs. Always return a fresh object.

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