随笔

2020-04-11

windows10自带unbutu16.4 LTS忘记root密码

1、进入Ubuntu，打开一个终端
2、sudo passwd root
3、输入新密码，确认密码。
4、修改密码成功，切换至管理员账号su root,输入新密码，成功

Ubuntu更改其他用户密码（如user）步骤：

1、进入Ubuntu，打开一个终端，输入 sudo su转为root用户。注意，必须先转为root用户！！！
2、sudo passwd user(user 是对应的用户名)
3、输入新密码，确认密码。
4、修改密码成功，重启，输入新密码进入Ubuntu

windows10自带unbutu16.4 LTS安装界面

切换清华源

备份源文件并更改源

1 2	sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak sudo vim /etc/apt/sources.list

把里面的都注释，然后直接把完整源放在文件后面

deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse

执行

1	sudo apt-get update

安装三个软件,xorg,xfce,xrdp

1
2
3

sudo apt-get install xorg
sudo apt-get install xfce4
sudo apt-get install xrdp

升级node 版本(linux)

npm install -g n
报错

1 2	npm ERR! notsup Unsupported platform for n@2.1.8: wanted {“os”:”!win32”,”arch”:”any”} (current: {“os”:”win32”,”arch”:”x64”})

解决方案

1	npm install -g n -force

创建react项目出错

1	internal/modules/cjs/loader.js:584

结局方案：删除npm系统文件夹内的node_modules中的create-react-app文件夹
然后执行命令

1 2	cnpm install -g create-react-app create-react-app my-app

React错误1 JSX表达式必须具有一个父元素。

Failed to compile
./src/TodoList.js
  Line 10:13:  Parsing error: Adjacent JSX elements must be wrapped in an enclosing tag. Did you want a JSX fragment <>...</>?

   8 |                 <input /><button>提交</button>
   9 |             </div>
> 10 |             <ul>
     |             ^
  11 |                 <li>学英语</li>
  12 |             </ul>
  13 |         )
This error occurred during the build time and cannot be dismissed.
问题原因：return必须整体包含在一个大的元素中。
解决办法:1,最外层手动添加一个标签
2.,React16中提供了Fragment标签

import React, {Component,Fragment} from ‘react’;
import { render } from ‘react-dom’;

class TodoList extends Component {
render(){
return (

学英语

Learning React

)
}
}
export default TodoList;

1
2
3

## React中得响应式设计思想和事件绑定
#
``

TypeError: Cannot read property ‘state’ of undefined
handleInputChange
D:/react/todolist/src/TodoList.js:33
30 | )
31 | }
32 | handleInputChange(e) {

33 | this.state.inputValue= e.target.value;
34 | // console.log(e.target.value);
35 | }
36 | }
View compiled▶ 22 stack frames were collapsed. This screen is visible only in development. It will not appear if the app crashes in production. Open your browser’s developer console to further inspect this error. Click the 'X' or hit ESC to dismiss this message.

this只想问题
console.log(this)打印指向
# JSX语法细节
编写注释
<Fragment>组件中
{//}
class替换为className
转义
dangerouslySetInnerHTML={{}}