Node.js--Koa基本使用

// demos/01.js
const Koa = require(‘koa‘);
const app = new Koa();

app.listen(3000);

// demos/02.js
const Koa = require(‘koa‘);
const app = new Koa();

const main = ctx => {
  ctx.response.body = ‘Hello World‘;
};

app.use(main);
app.listen(3000);

// demos/03.js
const main = ctx => {
  if (ctx.request.accepts(‘xml‘)) {
    ctx.response.type = ‘xml‘;
    ctx.response.body = ‘<data>Hello World</data>‘;
  } else if (ctx.request.accepts(‘json‘)) {
    ctx.response.type = ‘json‘;
    ctx.response.body = { data: ‘Hello World‘ };
  } else if (ctx.request.accepts(‘html‘)) {
    ctx.response.type = ‘html‘;
    ctx.response.body = ‘<p>Hello World</p>‘;
  } else {
    ctx.response.type = ‘text‘;
    ctx.response.body = ‘Hello World‘;
  }
};

// demos/04.js
const fs = require(‘fs‘);

const main = ctx => {
  ctx.response.type = ‘html‘;
  ctx.response.body = fs.createReadStream(‘./demos/template.html‘);
};

// demos/05.js
const main = ctx => {
  if (ctx.request.path !== ‘/‘) {
    ctx.response.type = ‘html‘;
    ctx.response.body = ‘<a href="/">Index Page</a>‘;
  } else {
    ctx.response.body = ‘Hello World‘;
  }
};

// demos/06.js
const route = require(‘koa-route‘);

const about = ctx => {
  ctx.response.type = ‘html‘;
  ctx.response.body = ‘<a href="/">Index Page</a>‘;
};

const main = ctx => {
  ctx.response.body = ‘Hello World‘;
};

app.use(route.get(‘/‘, main));

// demos/12.js
const path = require(‘path‘);
const serve = require(‘koa-static‘);

const main = serve(path.join(__dirname));
app.use(main);

// demos/13.js
const redirect = ctx => {
  ctx.response.redirect(‘/‘);
  ctx.response.body = ‘<a href="/">Index Page</a>‘;
};

app.use(route.get(‘/redirect‘, redirect));

// demos/07.js
const main = ctx => {
  console.log(`${Date.now()} ${ctx.request.method} ${ctx.request.url}`);
  ctx.response.body = ‘Hello World‘;
};

// demos/08.js
const logger = (ctx, next) => {
  console.log(`${Date.now()} ${ctx.request.method} ${ctx.request.url}`);
  next();
}
app.use(logger);

// demos/09.js
const one = (ctx, next) => {
  console.log(‘>> one‘);
  next();
  console.log(‘<< one‘);
}

const two = (ctx, next) => {
  console.log(‘>> two‘);
  next(); 
  console.log(‘<< two‘);
}

const three = (ctx, next) => {
  console.log(‘>> three‘);
  next();
  console.log(‘<< three‘);
}

app.use(one);
app.use(two);
app.use(three);

// demos/10.js
const fs = require(‘fs.promised‘);
const Koa = require(‘koa‘);
const app = new Koa();

const main = async function (ctx, next) {
  ctx.response.type = ‘html‘;
  ctx.response.body = await fs.readFile(‘./demos/template.html‘, ‘utf8‘);
};

app.use(main);
app.listen(3000);

// demos/11.js
const compose = require(‘koa-compose‘);

const logger = (ctx, next) => {
  console.log(`${Date.now()} ${ctx.request.method} ${ctx.request.url}`);
  next();
}

const main = ctx => {
  ctx.response.body = ‘Hello World‘;
};

const middlewares = compose([logger, main]);
app.use(middlewares);

// demos/14.js
const main = ctx => {
  ctx.throw(500);
};

// demos/15.js
const main = ctx => {
  ctx.response.status = 404;
  ctx.response.body = ‘Page Not Found‘;
};

// demos/16.js
const handler = async (ctx, next) => {
  try {
    await next();
  } catch (err) {
    ctx.response.status = err.statusCode || err.status || 500;
    ctx.response.body = {
      message: err.message
    };
  }
};

const main = ctx => {
  ctx.throw(500);
};

app.use(handler);
app.use(main);

// demos/17.js
const main = ctx => {
  ctx.throw(500);
};

app.on(‘error‘, (err, ctx) =>
  console.error(‘server error‘, err);
);

// demos/18.js`
const handler = async (ctx, next) => {
  try {
    await next();
  } catch (err) {
    ctx.response.status = err.statusCode || err.status || 500;
    ctx.response.type = ‘html‘;
    ctx.response.body = ‘<p>Something wrong, please contact administrator.</p>‘;
    ctx.app.emit(‘error‘, err, ctx);
  }
};

const main = ctx => {
  ctx.throw(500);
};

app.on(‘error‘, function(err) {
  console.log(‘logging error ‘, err.message);
  console.log(err);
});

// demos/19.js
const main = function(ctx) {
  const n = Number(ctx.cookies.get(‘view‘) || 0) + 1;
  ctx.cookies.set(‘view‘, n);
  ctx.response.body = n + ‘ views‘;
}

// demos/20.js
const koaBody = require(‘koa-body‘);

const main = async function(ctx) {
  const body = ctx.request.body;
  if (!body.name) ctx.throw(400, ‘.name required‘);
  ctx.body = { name: body.name };
};

app.use(koaBody());

// demos/21.js
const os = require(‘os‘);
const path = require(‘path‘);
const koaBody = require(‘koa-body‘);

const main = async function(ctx) {
  const tmpdir = os.tmpdir();
  const filePaths = [];
  const files = ctx.request.body.files || {};

  for (let key in files) {
    const file = files[key];
    const filePath = path.join(tmpdir, file.name);
    const reader = fs.createReadStream(file.path);
    const writer = fs.createWriteStream(filePath);
    reader.pipe(writer);
    filePaths.push(filePath);
  }

  ctx.body = filePaths;
};

app.use(koaBody({ multipart: true }));