在打字稿中替换Angular2的Elvis算子 [英] Replacement of Elvis Operator of Angular2 in Typescript
问题描述
在打字稿中是否有任何操作符使用similer到 elvis Operator of angular2，我的意思是说
让我知道我必须从对象获取密钥像这样：
Is there any operator in the typescript which is used similer to Elvis Operator of angular2, i mean to say
let supppose i have to get key from object like this:
this.myForm.name.first_name
如果first_name不存在则会抛出错误 first_name of undefined ，
and in case first_name does't exist so it will throw error first_name of undefined,
是的，我可以使用三元运算符这样的打字机来解决这个错误
yes i can handel this error using Ternary operator of typescript like this
this.myForm.name ? this.myForm.name.first_name : ''
但有时键太长，
所以在打字稿中有任何像 Elvis Operator 一样的运营商的angular2，这样我就可以这样使用了
so is there any operator like Elvis Operator of angular2 in the typescript so that i can use like this
this.myForm?.name?.first_name
推荐答案
TypeScript中没有elvis运算符，据我所知，也没有可比性。
There is no elvis operator in TypeScript and, as far as I know, nothing comparable, either.
有关参考，请参阅
的功能请求建议：安全导航操作员，即X？.Y 。 未实施的解释如下（在我看来， ，是一个有效的理由）：
For a reference see the feature request at Suggestion: "safe navigation operator", i.e. x?.y. The explanation for not implementing it is the following (which, in my opinion, is a valid reason):
现在关闭它。由于没有任何特定于TypeScript的内容需要在表达式级别上进行，因此这种大型操作员更改应该在ES规范委员会而不是在此处进行。
Closing this for now. Since there's not really anything TypeScript-specific that would require this at expression level, this kind of big operator change should happen at the ES spec committee rather than here.
一般重新评估这个问题的绊网将是一个具体的ES提案，进入下一阶段，或者ES委员会普遍认为这个特征很长时间不会发生（这样我们就可以定义我们自己的语义并合理地确定他们会赢）。
The general tripwires for re-evaluating this would be a concrete ES proposal reaching the next stage, or a general consensus from the ES committee that this feature wouldn't happen for a long time (so that we could define our own semantics and be reasonably sure that they would "win").
该表示法的替代方法是使用逻辑AND运算符，try / catch或辅助函数喜欢 getSafe（（）=> this.myForm.name.first_name），如这篇文章。
Alternatives to that notation would be to use the logical AND operator, try/catch or a helper function like getSafe(() => this.myForm.name.first_name) as described in this post.
更新2017年7月：正如JGFMK在评论中指出的那样，有一个名为 JavaScript的可选链接。如果/当提案到达阶段4时，它将被添加到语言规范中。
Update July 2017: As JGFMK pointed out in the comments, there is an ECMAScript proposal called Optional Chaining for JavaScript. If/when the proposal reaches Stage 4, it will be added to the language specification.
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