常见错误语法100例

- 日理万妓 2022-09-03 10:25 208阅读 0赞

###### *最新更新时间：2021年08月06日21:21:01* ######

#### [`《猛戳-查看我的博客地图-总有你意想不到的惊喜》`][-_-] ####

> 本文内容：程序员的基本功就是写代码，基本功的强弱决定了开发的效率和程序的后期运行bug率，本文记录自己在开发过程中遇到的一些语法错误，汇总以自省

## 快速创建元素为对象的非空数组 ##

*  错误示例，数组0号元素的key赋值后，数组每个元素的key都发生了变化

//看上去没有问题
    let tmpArr = new Array(5).fill({ key:'',value:''});
    //tmpArr [{key: "", value: ""},{key: "", value: ""},{key: "", value: ""},{key: "", value: ""},{key: "", value: ""},]
    tmpArr[0].key = 'eat';
    //tmpArr [{key: "eat", value: ""},{key: "eat", value: ""},{key: "eat", value: ""},{key: "eat", value: ""},{key: "eat", value: ""},]

*  正确示例，每次声明新的对象，防止引用被复用

let tmpArr = new Array(5).fill(null).map(()=>{ return { key:'',value:''}});
    //tmpArr [{key: "", value: ""},{key: "", value: ""},{key: "", value: ""},{key: "", value: ""},{key: "", value: ""},]
    tmpArr[0].key = 'eat';
    //tmpArr [{key: "eat", value: ""},{key: "", value: ""},{key: "", value: ""},{key: "", value: ""},{key: "", value: ""},]

## 快速复制数组 ##

*  错误示例，扩展运算符…是浅拷贝，导致`arr[0]`和`tmpArr[0]`指向了同一个地址

let arr = [{ name:'wan',age:18}];
    let tmpArr = [...arr];
    tmpArr[0].name = 'shao';
    //arr [{name:'shao',age:18}]
    //tmpArr [{name:'shao',age:18}]

*  正确示例，深拷贝

## 解构对象后，原对象的地址不会发生变化 ##

*  以为`obj.a`变成了`[]`，实际上a的指向发生变化不影响obj的指向

let obj = { a:{ name:'wan'}};
    let {  a } = obj;
    a = [];
    //obj.a {name:'wan'}

*  如果不是引用类型的数据，会同时被改变

let obj = { a:{ name:'wan'}};
    let {  a } = obj;
    a.name = [];
    //obj.a {name:[]}

## 后端写好接口，前端调用404 ##

*  接口一可以调通，接口二404

//后端代码
    
    //接口一
    @post('/save')
    async save() { 
      try { 
      
      } catch (e) { 
      
      } finally { 
      
      }
    }
    
    //接口二
    @get('queryById')
    async queryById() { 
      try { 
      
      } catch (e) { 
      
      } finally { 
      
      }
    }

*  经过仔细排查发现接口二写错了，缺少`/`，`'queryById'`应该是`'/queryById'`

#### 参考资料 ####

*  [createObjectURL][]

> 感谢阅读，欢迎评论^-^

## [`打赏我吧^-^`][-] ##

[-_-]: https://blog.csdn.net/wanshaobo888/article/details/79179440
[createObjectURL]: https://developer.mozilla.org/zh-CN/docs/Web/API/URL/createObjectURL
[-]: https://blog.csdn.net/wanshaobo888/article/details/86249460