log4js 库二次封装

log4js 安装与配置

1. 安装

```javascript
npm install log4js -D 
```

2. 封装示例

```javascript
/**
 * log4js 日志存储
 */
const log4js = require('log4js');
const levels = {
  'trace': log4js.levels.TRACE,
  'debug': log4js.levels.DEBUG,
  'info': log4js.levels.INFO,
  'warn': log4js.levels.WARN,
  'error': log4js.levels.ERROR,
  'fatal': log4js.levels.FATAL
};
log4js.configure({
  appenders: {
    console: { type: "console" }, // 输出到控制台
    info: {
      type: "dateFile", // 输出到文件内
      filename: "logs/info",
      pattern: 'yyyy-MM-dd.log',
      alwaysIncludePattern: true
    },
    error: {
      type: "dateFile", // 输出到文件内
      filename: "logs/error",
      pattern: 'yyyy-MM-dd.log',
      alwaysIncludePattern: true
    }
  },
  categories: { default: { appenders: ['console', 'info', 'error'], level: 'debug' } }
});
module.exports = log4js;
```