├── LICENSE
├── README.md
├── demo
├── README.md
├── assets
│ ├── content.html
│ ├── no-streams-solution.js
│ ├── script.js
│ └── styles.css
├── index.html
└── navigate.html
├── package-lock.json
├── package.json
├── polyfill
├── index.js
├── streaming-include.js
├── test
│ ├── assets
│ │ ├── blank.txt
│ │ ├── img.png
│ │ ├── script.js
│ │ ├── small-content-1.html
│ │ ├── small-content-2.html
│ │ └── style.css
│ ├── index.html
│ └── index.js
└── tsconfig.json
└── research.md
/LICENSE:
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/README.md:
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1 | # Streaming HTML parser and include
2 |
3 | This repo is exploring the idea of a [built-in module](https://github.com/tc39/ecma262/issues/395) that makes it easier to stream HTML content into a page.
4 |
5 | ## The problem
6 |
7 | Single page apps tend to follow this pattern on navigation:
8 |
9 | 1. Fetch all the content.
10 | 1. Display all the content.
11 |
12 | The lack of streaming in this solution can result in an experience [much slower than a server-rendered navigation](https://www.youtube.com/watch?v=4zG0AZRZD6Q).
13 |
14 | This repo aims to explore solutions that allow SPAs to stream content into the document.
15 |
16 | ## Current solutions & feature requests
17 |
18 | Most current solutions buffer content, but there are some hacky ways around it. These are covered in the [research](research.md).
19 |
20 | ## Low-level solution
21 |
22 | The aim is to create an API that generates elements from an HTML stream. Because the input can result in multiple elements being output, a transform stream feels like a good choice:
23 |
24 | ```js
25 | const response = await fetch(url);
26 | const domStream = response.body
27 | .pipeThrough(new TextDecoderStream())
28 | .pipeThrough(new HTMLParserStream());
29 | ```
30 |
31 | The stream yields `ParserChunk`s:
32 |
33 | ```js
34 | for await (const { node, parent, nextSibling } of domStream) {
35 | (parent || document.body).insertBefore(node, nextSibling);
36 | }
37 | ```
38 |
39 | * `node` - The newly created node.
40 | * `parent` - The node it should be inserted into. Null for top-level elements.
41 | * `nextSibling` - The node it should be inserted before. Null for elements that should be inserted as the last item of their parent.
42 |
43 | **Note:** The stream yields every node including descendants, not just top-level nodes. This means:
44 |
45 | * Once `HTMLParserStream` yields a node, it isn't going to add anything to it automatically.
46 | * Developers can modify nodes before they're adopted. This means they can change image urls before they're requested, or filter script nodes before they're executed.
47 |
48 | ## Mid-level solution
49 |
50 | ```js
51 | const writable = new DOMWritable(targetElement);
52 | ```
53 |
54 | * `targetElement` - The element to insert nodes into.
55 |
56 | This writable takes the output of `HTMLParserStream` and appends them into the `targetElement`.
57 |
58 | ```js
59 | const bodyWritable = new DOMWritable(targetElement);
60 | const response = await fetch(url);
61 | const domStream = response.body
62 | .pipeThrough(new TextDecoderStream())
63 | .pipeThrough(new HTMLParserStream())
64 | .pipeTo(bodyWritable);
65 | ```
66 |
67 | ## High-level solution
68 |
69 | A custom element.
70 |
71 | ```html
72 |
73 | ```
74 |
75 | It fetches the `src`, clears the content of the element, pipes the response through `TextDecoderStream`, `HTMLParserStream`, then adds resulting elements (as with `DOMWritable`) to itself.
76 |
77 | Attributes:
78 |
79 | * `src` - URL of the content. When `src` changes, any current stream is cancelled, and the above process starts again.
80 | * `crossorigin` - "anonymous" by default. Can be set to "use-credentials".
81 |
82 | Properties:
83 |
84 | * `src` and `crossOrigin` reflect their attributes.
85 | * `parsed` - A promise that resolves once the response has been fully read and elements created. Rejects if the fetch errors.
86 |
87 | If `src` is set (even to the same value), or `crossorigin` is set to a new value, any current stream is cancelled, and the loading process starts again.
88 |
89 | Methods:
90 |
91 | * `abort()` - Abort any current fetch.
92 |
93 | # Additional ideas
94 |
95 | There could also be a `DOMParserBlocker`:
96 |
97 | ```js
98 | const throttledDOMStream = domStream.passThrough(new DOMParserBlocker());
99 | ```
100 |
101 | This will apply the parser-blocking rules of scripts & stylesheets. Namely:
102 |
103 | * If a script-blocking stylesheet is passed through, it will hold-back any `
8 |
9 |
10 |
11 |
12 |