better-safe-typed-html

v1.0.1

Published

2 years ago

Type safe HTML JSX templates using TypeScript.

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nobu-mori

typescript html typesafe template

Typed HTML

HTML templates have never been this easy. Type safe using plain TypeScript with a minimal runtime footprint. No need to learn a template language, if you know TypeScript, you're set.

This:

// example.tsx
const item = 'item';
const icon = 'icon-add';
const ul = <ul>
    <li>{item}</li>
</ul>;

ul instanceof elements.RenderNode // true

const button = <button onclick="handleClick">
    <i class={icon}></i>
</button>;

button instanceof elements.RenderNode // true

console.log(ul.toString());
console.log(button.toString());

Prints:

<ul>
    <li>item</li>
</ul>
<button onclick="handleClick">
    <i class="icon-add"></i>
</button>

Getting started

Install:

npm install --save better-safe-typed-html

Configure your TypeScript compiler for JSX:

{
    "compilerOptions": {
        "jsx": "react",
        "jsxFactory": "elements.createElement"
    }
}

Although we're configuring the compiler to use React, this is not what is being used. Instead, we redirect all jsx element to typed-html's elements.createElement.

Now create a *.tsx file. For example: example.tsx with the following content:

// example.tsx
import * as elements from 'better-safe-typed-html';

const w = 'world';
const helloWorld = (<p>Hello <strong>{w}</strong></p>).toString();

typeof helloWorld; // => Just a string of course

However, the following piece of code will NOT compile:

<foo></foo>; // => Error: Property 'foo' does not exist on type 'JSX.IntrinsicElements'.
<a foo="bar"></a>; // => Error:  Property 'foo' does not exist on type 'HtmlAnchorTag'

Control flow

Conditional template with ?

<div>Random > 0.5: {Math.random() > .5 ? <strong>yes</strong> : 'no'}</div>

Repeat a template with Array.map

const items = ['item', 'item2'];
<ul>
    {items.map(i => <li>{i}</li>)}
</ul>;

Helper templates

Want a helper template? Just call a function

function listItem(n: number) {
    return <li>{n}</li>;
}
<ul>
    {[1, 2].map(listItem)}
</ul>

Using a helper template like an element

Want a helper component? Create a function that implements CustomElementHandler and you can call it like an HTML element.

import {Attributes, CustomElementHandler} from "typed-html"

function Button(attributes: Attributes | undefined, contents: string[]) {
    return <div><button type="button" class="original-class" {...attributes}>{contents}</button></div>;
}
// Or 
const Button: CustomElementHandler = (attributes, contents) => <div><button type="button" class="original-class" {...attributes}>{contents}</button></div>;
}
    
console.log((<Button style="color:#f00">Button Text</Button>).toString());

Prints:

<div>
    <button type="button" class="original-class" style="color:#f00">Button Text</button>
</div>

Sanitization

Strings are sanitized to remove HTML elements.

const script = '<script>alert("nice try!")</script>';
const body = <body>{script}</body>;

Will result in:

<body>&lt;script&gt;alert('nice try!');&lt;/script&gt;</body>

If you need sanitization, you can use something like sanitize-html.

Supported HTML

All HTML elements and attributes are supported, except for the svg.

Supported html elements: https://dev.w3.org/html5/html-author/#the-elements
Supported html events: http://htmlcss.wikia.com/wiki/HTML5_Event_Attributes

Missing an element or attribute? Please create an issue or a PR to add it. It's easy to add.

Void elements

Void elements (elements without closing tags) are supported, however you should close them in TypeScript.

const img = <img href="/foo/bar.png">; // => Error! JSX element 'img' has no corresponding closing tag.

In the example above, closing the image tag is required for valid TSX code:

const img = <img href="/foo/bar.png"></img>; // => '<img href="/foo/bar.png">'

See this code for a list of supported void elements.

Attribute types

All HTML attributes support a string value, however some attributes also support a number, Date or boolean(or absent value) type:

<meter value={1} min={0} max={5} low={1} high={4} optimum={3}></meter>; 
// => <meter value="1" min="0" max="5" low="1" high="4" optimum="3"></meter>
<ol start={3}></ol>;
<progress value={3} max={4}></progress>;
<td colspan={3} rowspan={3}></td>;
<th colspan={3} rowspan={3}></th>;

const date = new Date('1914-12-20T08:00');
<time datetime={date}></time>; 
// => <time datetime="1914-12-20T08:00:00.000Z"></time>
<ins datetime={date}>updated</ins>;
<del datetime={date}>old</del>;

// => <form> <input type="checkbox" checked> </form>
<form novalidate={false}> 
    <input type="checkbox" checked disabled={false}></input>
</form>

Custom elements

You can add custom elements by adding them to the intrinsic elements yourself:

// MyCustomElements.d.ts

declare namespace JSX {
    interface CustomElement {
        customAttribute?: string;
    }
    interface IntrinsicElements {
        myCustomElement: CustomElement;
    }
}

Now you can use it:

// UseCustomElement.ts
import * as elements from 'typed-html';

const myElement = <myCustomElement customAttribute="customValue"></myCustomElement>
console.log(myElement);

This prints:

<my-custom-element custom-attribute="customValue"></my-custom-element>

Custom attributes

Custom attribute names are already supported out-of-the-box for attributes with a dash (-) in the name. For example:

<button data-menu-item="3"></button>

Transformation

As a browser is case insensitive when it comes to element and attribute names, it is common practice to use kebab case for this. However <custom-element></custom-element> is not allowed in TypeScript. Therefore typed-html will transform <customElement></customElement> to <custom-element></custom-element>.

This transformation also works for custom attributes you define on a custom element yourself. For example:

<customElement aCustomAttr="value"></customElement>

Becomes

<custom-element a-custom-attr="value"></custom-element>

How this all works

The way this works is by using TypeScript's jsx support, but not for jsx/react interoperability. Instead, it defines the normal html tags as IntrinsicElements in the JSX namespace.

At runtime, the elements.createElement function is called for every html tag. It simply converts the given element to a string with minimal overhead.

This:

<ol start={2}>{[1, 2].map(i => <li>{i}</li>)}</ol>

Compiles to:

elements.createElement("ol", { start: 2 }, [1, 2].map(function (li) { 
    return elements.createElement("li", null, li); 
}));

Which translates to:

<ol start="2">
    <li>1</li>
    <li>2</li>
</ol>