Function arrByObj

arrByObj(arr, key, v?): {
[key: string]: any;
}
Parameters
- arr: {
  [key: string]: any;
  }[]
  
  需要作为转换后对象的key需要转换的数组
- key: string
  
  需要作为转换后对象的key
- v: string = ''
  对象的value取值，默认是数组的每一个元素作为值 @return: Object
```
 const arr = arr = [{name: 111, value: 222},{name: 333, value:444}]
 arrByObj(arr, 'name')   =>    {"111":{"name":111,"value":222},"333":{"name":333,"value":444}}
 arrByObj(arr, 'name', value)   =>    {"111":222,"333":444}
```
Returns {
[key: string]: any;
}
- [key: string]: any