9.3 KiB
title: Quick Start
Quick Start
This guide covers getting up and running with Egg using a real example. By following along with this guide step by step, you can quickly get started with Egg development.
Prerequisites
- Operating System: Linux, OS X or Windows (not recommended).
- Node.js Runtime: 6.x or newer; it is recommended that you use LTS Releases.
the Quick Way
To begin with, let's quickly initialize the project using a scaffold, which will quickly generate some of the major pieces of the application.
$ npm i egg-init -g
$ egg-init egg-example --type=simple
$ cd egg-example
$ npm i
Then get up and running using the following commands.
$ npm run dev
$ open localhost:7001
Step by Step
Usually you could just use egg-init of the last session, choose a scaffold that best fits your business model and quickly generate a project, then get started with the development.
However, in this section, instead of using scaffolds we will build a project called Egg HackerNews step by step, for a better understanding of how it works.
WARNING, TL;NR
Initialization
First let's create the project directory and initialize its structure.
$ mkdir egg-example
$ cd egg-example
$ npm init
$ npm i egg --save
$ npm i egg-bin --save-dev
Then add npm scripts to package.json.
{
"name": "egg-example",
"scripts": {
"dev": "egg-bin dev"
}
}
Create a Controller
If you are familiar with the MVC architecture, you might have already guessed that the first thing to create is a controller and router.
// app/controller/home.js
module.exports = function* home() {
this.body = 'hi, egg';
};
Then edit the router file and add a mapping.
// app/router.js
module.exports = app => {
app.get('/', 'home');
};
Now you can start up the Web Server and see your application in action.
$ npm run dev
$ open localhost:7001
Add Static Assets
Egg has a built-in plugin called static. In production, it is recommended that you deploy static assets to CDN instead of using this plugin.
static maps /public/* to the directory app/public/* by default.
In this case, we just need to put our static assets into the directory app/public.
app/public
├── css
│ └── news.css
└── js
├── lib.js
└── test.js
Add Templates for Rendering
In most cases, data are usually read, processed and rendered by the templates before being presented to the user. Thus we need to introduce corresponding template engines to handle it.
Egg does not force the use of any particular template engines, but instead specifies the View Plug-ins Specification to allow the developers to use different plug-ins for their individual needs.
In this example, we will use nunjucks.
First install the corresponding plug-in egg-view-nunjucks.
$ npm i egg-view-nunjucks --save
And enable it.
// config/plugin.js
exports.view = {
enable: true,
package: 'egg-view-nunjucks'
};
Then create a template for the index page. This usually goes to the app/view directory.
<!-- app/view/news/list.tpl -->
<html>
<head>
<title>Egg HackerNews Clone</title>
<link rel="stylesheet" href="/public/css/news.css" />
</head>
<body>
<div class="news-view view">
{% for item in list %}
<div class="item">
<a href="{{ item.url }}">{{ item.title }}</a>
</div>
{% endfor %}
</div>
</body>
<html/>
Then add a controller and router.
// app/controller/news.js
exports.list = function* newsList() {
const dataList = {
list: [
{ id: 1, title: 'this is news 1', url: '/news/1' },
{ id: 2, title: 'this is news 2', url: '/news/2' }
]
};
yield this.render('news/list.tpl', dataList);
};
// app/router.js
module.exports = app => {
app.get('/', 'home');
app.get('/news', 'news.list');
};
Open a browser window and navigate to http://localhost:7001/news. You should be able to see the rendered page.
Tip：In development, Egg enables the development plug-in by default, which reloads your worker process when changes are made to your back-end code.
Create a Service
In practice, controllers usually won't generate data on their own, neither will they contain complicated business logic. Complicated business logic should instead be abstracted as a busineess logic layer, i.e., service.
Let's create a service to fetch data from the HackerNews.
// app/service/news.js
module.exports = app => {
class NewsService extends app.Service {
* list(page = 1) {
// read config
const { serverUrl, pageSize } = this.app.config.new;
// use build-in http clinet, see https://www.npmjs.com/package/urllib
// GET hacker-news api
const { data: idList } = yield this.ctx.curl(`${serverUrl}/topstories.json`, {
data: {
orderBy: '"$key"',
startAt: `"${pageSize * (page - 1)}"`,
endAt: `"${pageSize * page - 1}"`,
},
dataType: 'json',
});
// parallel GET detail , see `yield {}` from co
const newsList = yield Object.keys(idList).map(key => {
const url = `${serverUrl}/item/${idList[key]}.json`;
return this.ctx.curl(url, { dataType: 'json' }).then(res => res.data);
});
return newsList;
}
}
return NewsService;
};
Egg has urllib built in in order to help you make http requests.
Then slightly modify our previous controller.
// app/controller/news.js
exports.list = function* newsList() {
const page = this.query.page || 1;
const newsList = yield this.service.news.list(page);
yield this.render('news/list.tpl', { list: newsList });
};
Add Extensions
We might encounter a small problem here. The time that we fetched are in Unix Time, whereas we want to present them in a more friendly way to read.
Egg provides us with a quick way to extend its functionalities.
We just need to add extension scripts to the app/extend directory.
For more information, cf. Extensions.
In the case of egg-view-nunjucks, we can just write a helper as an extension.
// app/extend/helper.js
const moment = require('moment');
exports.relativeTime = time => moment(new Date(time * 1000)).fromNow();
Then use it in the templates.
<!-- app/views/news/list.tpl -->
{{ helper.relativeTime(item.time) }}
Add Middlewares
Suppose that we wanted to prohibit accesses from Baidu crawlers.
Smart developers might quickly guess that we can achieve it by adding a middleware that checks the User-Agent.
// app/middleware/robot.js
// options === app.config.robot
module.exports = (options, app) => {
return function* robotMiddleware(next) {
const source = this.get('user-agent') || '';
const match = options.ua.some(ua => ua.test(source));
if (match) {
this.status = 403;
this.message = 'go away, robot';
} else {
yield next;
}
}
};
// config/config.default.js
// mount middleware
exports.middleware = [
'robot'
];
// middleware config
exports.robot = {
ua: [
/Baiduspider/i,
]
};
Now try it using curl localhost:7001/news -A "Baiduspider".
Add Configurations
When writing business logic, it is inevitable that we need to manage configurations. Egg provides a powerful way to manage them in a merged configuration file.
- Environment-specific configuration files are well supported, e.g. config.local.js, config.prod.js, etc.
- Configurations could happen wherever convenient, e.g. near Applications/Plug-ins/Framesworks, and Egg will take care of merging and loading them.
- For more information on merging, see Configurations.
// config/config.default.js
exports.robot = {
ua: [
/curl/i,
/Baiduspider/i,
],
};
// config/config.local.js
// only read at development mode, will override default
exports.robot = {
ua: [
/Baiduspider/i,
],
};
// app/controller/news.js
exports.list = function* newsList() {
const config = this.app.config.news;
};
Conclusions
We can only touch the tip of the iceberg of Egg with the above short sections. We recommend that developers continue reading other documents:
- Egg provides a powerful mechanism for extending features. See Plug-ins.
- As large teams need to follow certain constraints and conventions, in egg, we recommend further creating an upper-level framework that fits your team. See Frameworks.
- In Egg, writing unit tests is highly recommended, and it actually turns out to be very straightforward. See Unit Testing.