0a1eeea424
* fix: replace sh with shell fix replace terminal with shell fix replace node with js fix replace output with shell fix replace cs with csharp fix replace c++ with cpp fix replace c# with csharp fix replace javasctipt with js fix replace syntax with js fix replace unix with shell fix replace linux with shell fix replace java 8 with java fix replace swift4 with swift fix replace react.js with jsx fix replace javascriot with js fix replace javacsript with js fix replace c++ - with cpp fix: corrected various typos fix: replace Algorithm with nothing fix: replace xaml with xml fix: replace solidity with nothing fix: replace c++ with cpp fix: replace txt with shell fix: replace code with json and css fix: replace console with shell
75 lines
1.8 KiB
Markdown
75 lines
1.8 KiB
Markdown
---
|
||
title: With
|
||
localeTitle: 同
|
||
---
|
||
## 同
|
||
|
||
JavaScript的`with`语句是在一个对象上编辑多个属性的简便方法。大多数开发人员不鼓励使用`with` ，您最好不要使用此关键字。
|
||
|
||
**注意** ： `"strict mode"`禁止使用`with` 。
|
||
|
||
### 句法
|
||
|
||
```js
|
||
with (expression)
|
||
statement
|
||
```
|
||
|
||
### 示例用法
|
||
|
||
在JavaScript中，您可以单独修改对象的属性，如下所示：
|
||
|
||
```javascript
|
||
let earth = {};
|
||
earth.moons = 1;
|
||
earth.continents = 7;
|
||
```
|
||
|
||
`with`为您提供了修改对象属性的简写：
|
||
|
||
```javascript
|
||
with (earth) {
|
||
moons = 1;
|
||
continents = 7;
|
||
}
|
||
```
|
||
|
||
虽然这个例子很做作，你能理解的用例`with`更多，如果你有更大的物体象下面这样：
|
||
|
||
```javascript
|
||
earth.continents.australia.geography.ocean = "Pacific";
|
||
earth.continents.australia.geography.river = "Murray";
|
||
earth.continents.australia.geography.mountain = "Kosciuszko";
|
||
```
|
||
|
||
### 备择方案
|
||
|
||
你不应该使用它`with`因为它有微妙的错误和兼容性问题。强烈推荐的方法是将对象分配给变量，然后修改变量的属性。以下是使用更大对象的示例：
|
||
|
||
```javascript
|
||
let earth = {
|
||
continents: {
|
||
australia: {
|
||
geography: {}
|
||
}
|
||
}
|
||
};
|
||
|
||
let geo = earth.continents.australia.geography;
|
||
|
||
geo.ocean = "Pacific";
|
||
geo.river = "Murray";
|
||
geo.mountain = "Kosciuszko";
|
||
```
|
||
|
||
### 试试看
|
||
|
||
https://repl.it/Mixg/5
|
||
|
||
#### 更多信息：
|
||
|
||
[https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/with](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/with)
|
||
|
||
[https://yuiblog.com/blog/2006/04/11/with-statement-considered-harmful/](https://yuiblog.com/blog/2006/04/11/with-statement-considered-harmful/)
|
||
|
||
[http://2ality.com/2011/06/with-statement.html](http://2ality.com/2011/06/with-statement.html) |