Divulge HN: Allotment 1 make your contain JavaScript framework

Divulge HN: Allotment 1 make your contain JavaScript framework

Be taught by building your contain React clone

After I don’t realize something absolutely, I try and ruin things down. Runt by runt.

Unusual things pop up the total time, so belief the fundamental building blocks will home you aside as a consequence of you’ll perceive how things indubitably work.

In advise to fancy how React works, let’s declare ourselves and write our contain React from scratch.

The high-level aim for this text is to make a semi-optimized React. You are going to learn how one can spend JSX independently of React and the contrivance in which one can impact your contain digital DOM and render it.

Here is the three-step pipeline we’re building:


  1. Setup JSX: so that we are able to retailer Digital DOM representations of the rendered DOM. As a bonus, JSX enables us to declaratively spend JS techniques similar to .design((x)=> ... in the template.
  2. Digital DOM: Convert JSX to a Javascript representation of the staunch rendered DOM tree. By enforcing our containcreateElementwe can see how one can convert JSX to JS knowledge constructions. The fleshy representation of our rendered web page will be saved in JS. This representation is idea as the Digital DOM.
  3. Rendering: In the extinguish, the Digital DOM representations are converted into valid DOM aspects and genuinely rendered on the web page.

By the end of this series, you are going to change into conversant in Digital DOM, knowledge binding, and commerce detection. You’ll see in the abet of the scenes what is occurring, and be to your formula to changing into the most badass version of your self. In the next article I will hide building useState hooks and commerce detection.

Let’s walk ahead and knock this setup out.

I obtained’t try and hide every fragment in-depth. In the event you treasure to dig deeper, many sections beneath contain hyperlinks to deep dive sources.

1.1 Folder setup

Budge these commands to your terminal to impact a fresh folder, add typescript, and bundle with parcel. (Deep Dive: Behold right here)

mkdir mini-react-series && cd mini-react-series && memoir add typescript parcel -D

1.2. Generate a TSconfig file for Typescript

tsc --init

  • if that expose doesn’t work make determined that you simply secure typescript build in npm set up typescript -g

1.3. Setup JSX

JSX is a syntax extension for JavaScript that lets you write HTML-treasure markup internal a JavaScript file. We spend Babel to transpile JSX to HTML.

  • Set up Babel

npm i @babel/plugin-transform-react-jsx

  • Update your babel config file to make spend of our framework’s implementation of createElement. To impact this, walk to the .babelrc file and update the pragma property (as confirmed beneath) so that it makes spend of our framework’s soon-to-be-created createElement.
"plugins": [
["@babel/plugin-transform-react-jsx", {
"pragma": "MiniFramework.createElement", // default pragma is React.createElement
"throwIfNamespace": false // defaults to true

1.4. Budge it

memoir parcel index.html

Our rendering engine is in accordance to JSX andcreateElement. Nonetheless, what precisely is JSX andcreateElement and why will we want it?

The rationale of createElement is to convert JSX to our contain knowledge structure/replica of every DOM component. Here is idea as the “Digital DOM”. (deep dive):

JSX -> Digital DOM -> DOM

“Digital DOM” is solely the DOM you protect in Javascript make for diffing and optimizing your commerce detection cycle. Judge it as your framework’s non-public replica of the DOM in JS format.

2.1 Put into effect React’s createElement to retailer JS Digital DOM

Outline a JSX component in a tsx file index.tsx and let Babel cope with the remainder.

const jsxElement=(

Hello, world!


Babel will get hold of every JSX component in all of our *.tsx recordsdata and contact createElement()

After calling createElement a digital DOM representation of the DOM component is returned vDOMElement and saved in a JS object.

const vDOMElement=createElement(
{ className: "greeting" },
"Hello, world!"

As you would possibly perhaps presumably well be ready to see above, there are 3 arguments to the createElement formula:

  • Argument 1: is the mark title "h1"
  • Argument 2: is an object with all the component’s properties. On this example, it is correct the CSS class: { className: “greeting” },
  • Argument 3: Are the formative years nodes of the given JSX component. On this case, it is correct a textual stutter node that says “Hello, world!”

2.2 Initialize our framework object in index.tsx

Now, let’s implement our containcreateElement that accepts these 3 arguments and converts JSX to the Digital DOM.

Kind a object that has the createElement formula. I chose to name this framework MiniFramework :

As you would possibly perhaps presumably well be ready to see, createElement returns an component that has 4 properties:

  • Property 1: the mark / JSX component
  • Property 2: the mark form
  • Property 3: props which holds the component’s properties such because the className or enter values. The formative years are the baby aspects and we can iterate over them later and render every of them recursively.

Rendering is largely the direction of of taking JSX aspects with their properties and constructing the staunch DOM.

Digital DOM -> Rendering

Let’s implement rendering so that we are able to bewitch any Digital DOM representation and genuinely hide it on the quilt hide.

3.1 Kind a index.html file:

  • add a

    in index.html. Here is the container component where the app will be rendered.

  • contain a script hyperlink to the index.tsx file that we created earlier.

3.2 Put into effect render

Let’s implement our render formula that would possibly perhaps presumably well also bewitch 2 arguments:

const render=(frameworkEl: FrameworkEl, container: Ingredient | null)=> { .... }
  • Argument 1: the digital DOM component to render frameworkEl.
  • Argument 2: the container component where all the pieces will be rendered internal. (Purchase that we created

    in index.html )

Here’s what every line does:

  • Kind easy aspects when JSX is correct textual stuttertraces 2–10: If we bump into a string or quantity, then all we must impact is impact a textual stutter nodes with doc.createTextNode(...).
  • Initialize a valid DOM Ingredient traces 11: we impact a valid component that we can apply properties to and render.
  • Determine properties from JSX Ingredient and Direct it to the valid component traces 14–18: To make determined that that theactualDOMElement has the the same classes, ids, worth, etc we can loop by the props of the JSX component and apply it to the actualDOMElement .
  • Repeat above for every child node traces: 26–30: recursively accelerate by every child and impact the steps above

We made it, all that’s left is to name our render formula. Concretely, right here’s what it appears to be like treasure if you namerender :

MiniFramework.render(vDOMElement, doc.querySelector(“#app”));

Which is the the same as React’s:

To recap, we secure completed this pipeline:



In the next article, you are going to learn how one can implement commerce detection and React’s useState hook.

Rather than re-rendering / replacing all aspects, we can surgically exchange solely the component that changed when setState is idea as. We can spend our Digital DOM to review and exchange the rest that changed.

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Ava Chan

Ava Chan

I'm a researcher at Utokyo :) and a big fan of Ava Max