JS框架 -（一）fetch async await 模块 npm

作业内容：

1. 实例演示fetch api, async,await的使用

      // cps ：尾部调用, 让用户产生一个错觉, 代码是同步执行,并不异步
      // 异步操作：定时器, 文件操作, 网络操作
      function createdFile(success, failure) {
        success();
        failure();
      }
      function success(msg) {
        return "success" + msg;
      }
      function failure(msg) {
        return "error" + msg;
      }

//createdFile().then(success).then(json).catch(failure)
      fetch("https://jsonplaceholder.typicode.com/todos/1")
        .then((response) => response.json())
        .then((json) => console.log(json));
      url = "http://tptest.com/users.php";
      async function getInfo(btn,url) {
        response = await fetch(url)
        result = await response.json();
        render(result, btn)
      }
      //模块
      <script type="module">
      // 模块: 就是一个外部的js
      // 传统js,引入外部js,共享一个全局空间
      // 模块有自己的独立作用域
      // 导入模块
      // import 成员列表 from 模块路径
      import * as m from "./1.js";
      console.log(m.email);
      console.log(new m.Demo().show());
    </script>

2. npm 安装与删除包的常用操作

"axios": "^0.26.1"
0: 大版本
26:小版本
1: 补丁
^: 仅允许小版本更新
*: 允许大版本更新
~: 仅允许修复补丁
npm i axios -S: 生产依赖
npm i axios -D:开发依赖
npm root -g: 查看全局模块的路径

Windows PowerShell
PS E:\php19\0413> node 2.js
admin@php.cn
PS E:\php19\0413> npm -v  
PS E:\php19\0413> npm init -y
Wrote to E:\php19\0413\package.json:
{
  "name": "0413",
  "version": "1.0.0",
  "description": "",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC"
}
PS E:\php19\0413> npm install axios
added 2 packages, and audited 3 packages in 7s
1 package is looking for funding
  run `npm fund` for details
found 0 vulnerabilities
PS E:\php19\0413> npm uninstall axios
removed 2 packages, and audited 1 package in 603ms
found 0 vulnerabilities

3. node中的模块声明,导出与导入

const { site } = require('./m1');
//require导入
http = require('http');
//console.log(http);
mysite = require('./m1.js')
console.log(mysite.site);
console.log(mysite.getSite());
//常用导出
module.exports = {
    site: '第19期学习',
    getSite() {
      return this.site + ' (php.cn)';
    },
  };
//文件模块
fs = require('fs')
fs.readFile('./test.txt', function (err, data) { 
    if (err) {
        return false
    } else {
        console.log(String(data));
        console.log(data.toString());
    }
})