直播app开发，使用koa和MongoDB实现分页和模糊查询

1. 分页

per_page：一页多少条数据

page：第几页

// index.js<br>const Koa = require('koa')<br>const app = new Koa()<br>const Router = require('koa-router')<br>const usersRouter = new Router({ prefix: '/users'})<br>// MongoDB数据库User模型<br>const User = require('/models/users.js')<br> <br>const bodyparser = require('koa-bodyparser')<br>app.use(bodyparser()) <br> <br>// 用户列表<br>usersRouter.get('/', (ctx) => { <br>    // 分页 http://localhost:3000/users?page=2&per_page=3<br>    const { per_page = 10 } = ctx.query<br>    const page = Math.max(ctx.query.page * 1, 1) - 1<br>    const perPage = Math.max(per_page * 1, 1)<br>    ctx.body = await User.find().limit(perPage).skip(page * perPage)<br>})<br> <br>app.use(usersRouter.routes())<br>app.use(usersRouter.allowedMethods())<br> <br>app.listen(3000)

2. 模糊查询

MongoDB中实现模糊查询要使用正则表达式

<br>// index.js<br>const Koa = require('koa')<br>const app = new Koa()<br>const Router = require('koa-router')<br>const usersRouter = new Router({ prefix: '/users'})<br>// MongoDB数据库User模型<br>const User = require('/models/users.js')<br> <br>const bodyparser = require('koa-bodyparser')<br>app.use(bodyparser()) <br> <br>// 用户列表<br>usersRouter.get('/', (ctx) => { <br>    // 分页+模糊查询 http://localhost:3000/users?page=1&per_page=3&q=李<br>    const { per_page = 10 } = ctx.query<br>    const page = Math.max(ctx.query.page * 1, 1) - 1<br>    const perPage = Math.max(per_page * 1, 1)<br>    // 模糊查询，要用正则表达式<br>    ctx.body = await User.find({name:new RegExp(ctx.query.q)}).limit(perPage).skip(page * perPage)<br>})<br> <br>app.use(usersRouter.routes())<br>app.use(usersRouter.allowedMethods())<br> <br>app.listen(3000)

3. 字段过滤

select 用于显示在MongoDB数据库中select:false默认不显示，但是现在需要显示的数据

// index.js<br>const Koa = require('koa')<br>const app = new Koa()<br>const Router = require('koa-router')<br>const usersRouter = new Router({ prefix: '/users'})<br>// MongoDB数据库User模型<br>const User = require('/models/users.js')<br> <br>const bodyparser = require('koa-bodyparser')<br>app.use(bodyparser()) <br> <br>// 根据用户id查询某个用户<br>usersRouter.get('/:id', (ctx) => { <br>    // 字段过滤 http://localhost:3000/users/6268c33f5ecce8e573b27366?fields=educations;business<br>    const { fields = '' } = ctx.query<br>    const selectFields = fields.split(';').filter(f => f).map(f => ' +' + f).join(' ') //注意这里是空格+<br>    const populateStr = fields.split(';').filter(f => f).map(f => {<br>        if (f === 'employments') {<br>            return 'employments.company employments.job'<br>        }<br>        if (f === 'educations') {<br>            return 'educations.school educations.major'<br>        }<br>        return f<br>    }).join(' ')<br>    const user = await User.findById(ctx.params.id).select(selectFields).populate(populateStr)<br>    if (!user) {<br>        ctx.throw(404, '用户不存在')<br>    }<br>    ctx.body = user<br>})<br> <br>app.use(usersRouter.routes())<br>app.use(usersRouter.allowedMethods())<br> <br>app.listen(3000)

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