104 lines
		
	
	
		
			3.7 KiB
		
	
	
	
		
			Markdown
		
	
	
	
	
	
			
		
		
	
	
			104 lines
		
	
	
		
			3.7 KiB
		
	
	
	
		
			Markdown
		
	
	
	
	
	
---
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date: "2021-10-13T16:00:00+02:00"
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title: "Guidelines for Frontend Development"
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slug: "guidelines-frontend"
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weight: 20
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toc: false
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draft: false
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menu:
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  sidebar:
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    parent: "developers"
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    name: "Guidelines for Frontend"
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    weight: 20
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    identifier: "guidelines-frontend"
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---
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# Guidelines for Frontend Development
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**Table of Contents**
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{{< toc >}}
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## Background
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Gitea uses [Less CSS](https://lesscss.org), [Fomantic-UI](https://fomantic-ui.com/introduction/getting-started.html) (based on [jQuery](https://api.jquery.com)) and [Vue2](https://vuejs.org/v2/guide/) for its frontend.
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The HTML pages are rendered by [Go HTML Template](https://pkg.go.dev/html/template)
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## General Guidelines
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We recommend [Google HTML/CSS Style Guide](https://google.github.io/styleguide/htmlcssguide.html) and [Google JavaScript Style Guide](https://google.github.io/styleguide/jsguide.html)
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### Gitea specific guidelines:
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1. Every feature (Fomantic-UI/jQuery module) should be put in separate files/directories.
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2. HTML ids and classes should use kebab-case.
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3. HTML ids and classes used in JavaScript should be unique for the whole project, and should contain 2-3 feature related keywords. We recommend to use the `js-` prefix for classes that are only used in JavaScript.
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4. jQuery events across different features should use their own namespaces.
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5. CSS styling for classes provided by frameworks should not be overwritten. Always use new class-names to overwrite framework styles. We recommend to use the `us-` prefix for user defined styles.  
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6. The backend can pass complex data to the frontend by using `ctx.PageData["myModuleData"] = map[]{}`
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7. Simple pages and SEO-related pages use Go HTML Template render to generate static Fomantic-UI HTML output. Complex pages can use Vue2 (or Vue3 in future).
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### `async` Functions
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Only mark a function as `async` if and only if there are `await` calls 
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or `Promise` returns inside the function.
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It's not recommended to use `async` event listeners, which may lead to problems. 
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The reason is that the code after await is executed outside the event dispatch. 
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Reference: https://github.com/github/eslint-plugin-github/blob/main/docs/rules/async-preventdefault.md
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If we want to call an `async` function in a non-async context,
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it's recommended to use `const _promise = asyncFoo()` to tell readers
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that this is done by purpose, we want to call the async function and ignore the Promise.
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Some lint rules and IDEs also have warnings if the returned Promise is not handled.
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#### DOM Event Listener
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```js
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el.addEventListener('click', (e) => {
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  (async () => {
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    await asyncFoo(); // recommended
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    // then we shound't do e.preventDefault() after await, no effect
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  })(); 
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  const _promise = asyncFoo(); // recommended
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  e.preventDefault(); // correct
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});
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el.addEventListener('async', async (e) => { // not recommended but acceptable
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  e.preventDefault(); // acceptable
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  await asyncFoo();   // skip out event dispath 
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  e.preventDefault(); // WRONG
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});
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```
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#### jQuery Event Listener
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```js
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$('#el').on('click', (e) => {
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  (async () => {
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    await asyncFoo(); // recommended
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    // then we shound't do e.preventDefault() after await, no effect
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  })();
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  const _promise = asyncFoo(); // recommended
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  e.preventDefault();  // correct
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  return false;        // correct
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});
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$('#el').on('click', async (e) => {  // not recommended but acceptable
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  e.preventDefault();  // acceptable
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  return false;        // WRONG, jQuery expects the returned value is a boolean, not a Promise
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  await asyncFoo();    // skip out event dispath
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  return false;        // WRONG
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});
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```
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### Vue2/Vue3 and JSX
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Gitea is using Vue2 now, we plan to upgrade to Vue3. We decided not to introduce JSX to keep the HTML and the JavaScript code separated.
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