building-a-rich-text-editor-with-lit
Learn how to build a rich text editor using a Lit web component, complete with a toolbar for formatting text, links, and styles.
What this skill does
# Building a Rich Text Editor with Lit
In this article I will go over how to set up a [Lit](https://lit.dev/) web component and use it to create a rich text editor.
> **TLDR** The final source [here](https://github.com/rodydavis/lit-html-editor) and an online [demo](https://rodydavis.github.io/lit-html-editor/).
## Prerequisites
* Vscode
* Node >= 16
* Typescript
## Getting Started
We can start off by navigating in terminal to the location of the project and run the following:
```
npm init @vitejs/app --template lit-ts
```
Then enter a project name `lit-rich-text-editor` and now open the project in vscode and install the dependencies:
```
cd lit-rich-text-editor
npm i @material/mwc-icon-button
npm i -D @types/node
code .
```
Update the `vite.config.ts` with the following:
```
import { defineConfig } from "vite";
import { resolve } from "path";
export default defineConfig({
base: '/lit-rich-text-editor/',
build: {
lib: {
entry: "src/lit-rich-text-editor.ts",
formats: ["es"],
},
rollupOptions: {
input: {
main: resolve(__dirname, "index.html"),
},
},
},
});
```
## Template
Open up the `index.html` and update it with the following:
```
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<link rel="icon" type="image/svg+xml" href="/src/favicon.svg" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<link
href="https://fonts.googleapis.com/css?family=Material+Icons&display=block"
rel="stylesheet"
/>
<title>Lit Rich Text Editor</title>
<script type="module" src="/src/lit-rich-text-editor.ts"></script>
<style>
body {
padding: 0;
margin: 0;
}
lit-rich-text-editor {
--editor-width: 100%;
--editor-height: 100vh;
}
</style>
</head>
<body>
<lit-rich-text-editor>
<template>
<h1>Headline 1</h1>
<p>This is a paragraph.</p>
<p>
<span style="background-color: rgb(255, 0, 0)"
><font color="#ffffff">Styled Text</font></span
>
</p>
<p>
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do
eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad
minim veniam, quis nostrud exercitation ullamco laboris nisi ut
aliquip ex ea commodo consequat. Duis aute irure dolor in
reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla
pariatur. Excepteur sint occaecat cupidatat non proident, sunt in
culpa qui officia deserunt mollit anim id est laborum.
</p>
</template>
</lit-rich-text-editor>
</body>
</html>
```
The important things to take away are the styles added to remove the body padding and send size [CSS Custom Properties](https://developer.mozilla.org/en-US/docs/Web/CSS/--*) to the editor to take up the full viewport.
Inside the `lit-rich-text-editor` tags there is a [`template`](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/template) passed as a slot to provide html that will not be rendered but can be accessed.
There is also an import for the [Material Icons](https://fonts.google.com/icons) so it can be used in the editor later.
## Editor
The next thing to create is the editor itself. Open up `src/lit-rich-text-editor.ts` and update it with the following:
```
import { html, css, LitElement } from "lit";
import { customElement, property, state } from "lit/decorators.js";
import "@material/mwc-icon-button";
@customElement("lit-rich-text-editor")
export class LitRichTextEditor extends LitElement {
@state() content: string = "";
@state() root: Element | null = null;
static styles = css`
:host {
--editor-width: 600px;
--editor-height: 600px;
--editor-background: #f1f1f1;
--editor-toolbar-height: 33px;
--editor-toolbar-background: black;
--editor-toolbar-on-background: white;
--editor-toolbar-on-active-background: #a4a4a4;
}
main {
width: var(--editor-width);
height: var(--editor-height);
display: grid;
grid-template-areas:
"toolbar toolbar"
"editor editor";
grid-template-rows: var(--editor-toolbar-height) auto;
grid-template-columns: auto auto;
}
#editor-actions {
grid-area: toolbar;
width: var(--editor-width);
height: var(--editor-toolbar-height);
background-color: var(--editor-toolbar-background);
color: var(--editor-toolbar-on-background);
overscroll-behavior: contain;
overflow-y: auto;
-ms-overflow-style: none;
scrollbar-width: none;
}
#editor-actions::-webkit-scrollbar {
display: none;
}
#editor {
width: var(--editor-width);
grid-area: editor;
background-color: var(--editor-background);
}
#toolbar {
width: 1090px;
height: var(--editor-toolbar-height);
}
[contenteditable] {
outline: 0px solid transparent;
}
#toolbar > mwc-icon-button {
color: var(--editor-toolbar-on-background);
--mdc-icon-size: 20px;
--mdc-icon-button-size: 30px;
cursor: pointer;
}
#toolbar > .active {
color: var(--editor-toolbar-on-active-background);
}
select {
margin-top: 5px;
height: calc(var(--editor-toolbar-height) - 10px);
}
input[type="color"] {
height: calc(var(--editor-toolbar-height) - 15px);
-webkit-appearance: none;
border: none;
width: 22px;
}
input[type="color"]::-webkit-color-swatch-wrapper {
padding: 0;
}
input[type="color"]::-webkit-color-swatch {
border: none;
}
`;
render() {
return html`<main>
<input id="bg" type="color" style="display:none" />
<input id="fg" type="color" style="display:none" />
<div id="editor-actions">
<div id="toolbar">
</div>
</div>
<div id="editor">${this.root}</div>
</main> `;
}
async firstUpdated() {
const elem = this.parentElement!.querySelector("lit-rich-text-editor template");
this.content = elem?.innerHTML ?? "";
this.reset();
}
reset() {
const parser = new DOMParser();
const doc = parser.parseFromString(this.content, "text/html");
document.execCommand("defaultParagraphSeparator", false, "br");
document.addEventListener("selectionchange", () => {
this.requestUpdate();
});
const root = doc.querySelector("body");
root!.setAttribute("contenteditable", "true");
this.root = root;
}
}
```
With everything updated run `npm run dev` and the following should appear in the browser:
Nothing special is happening yet, but the template is being read and passed into the element, parsed and setting the [`contenteditable`](https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/contenteditable) attribute to `true`.
This is a way to access the slots and use the nodes to hold data that are not used for rendering. Doing it this way allows for a transformation of the HTML source into a format that can be used.
## Toolbar
At the bottom of the class before the last `}` add the following:
```
renderToolbar(command: (c: string, val: string | undefined) => void) {
// TODO: Selection does not work on Safari iOS
const selection = this.shadowRoot?.getSelection
? this.shadowRoot!.getSelection()
: null;
const tags: string[] = [];
if (selection?.type === "Range") {
// @ts-ignore
let parentNode = selection?.baseNode;
if (parentNode) {
const checkNode = () => {
const parentTagName = parentNode?.tagName?.toLowerCase()?.trim();
if (parentTagName) tags.push(parentTagName);
};
while (parentNode != null) {
checkNode();
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