单行 if vs &&在 JavaScript 中

2022-01-20 00:00:00 logical-operators if-statement conditional javascript

两者之间有什么有意义的区别

Is there any meaningful difference between

condition && console.log("this may run");

和

if (condition) console.log("this may run);

如果不是，最佳做法是什么?

If not, which is a best practice?

推荐答案

你应该使用第二个.

您的代码应该说明它的含义.这就是编写语义"代码的含义.如果您正在编写 if 条件，那么您应该使用 if 语句，因为这就是它的用途.&& 在语义上是一个逻辑与，应该在您对两个值的逻辑连接产生的逻辑值感兴趣的情况下使用.

Your code should say what it means. That is what is meant by writing "semantic" code. If you are writing an if condition, then you should use the if statement, because that's what it is there for. The && is, semantically, a logical and, which should be used in cases where you are interested in the logical value resulting from the logical conjunction of two values.

正如其他答案所建议的那样，编写语义代码可以更容易地编写、理解和维护.就这条评论而言:

Writing semantic code, as other answers have suggested, makes it easier to write and understand and maintain. As far as this comment goes:

如果其他人可能需要阅读或维护它，请使用第二个.

If someone else may need to read or maintain it, then use the second.

请记住，六个月后的你"是其他人".

Remember that "you six months from now" is "someone else".

当您的意思是 if 时，以下是使用 if 的一些具体原因:

Here are some specific reason for using if when you mean if:

  1. 如果你想添加一个 else 子句，你可以添加它.如果你写了 a &&b 那么您将不得不将其重写为 a ?b : c.

  1. If you want to add an else clause, you can just add it. If you have written a && b then you will have to rewrite it as a ? b : c.

假设你使用了花括号，如 if (a) { b;}，那么你可以很容易地在body中添加另一个步骤，通过编写if (a) { b;C;}.如果你写了 a &&b，那么您需要将其重写为 a &&(b, c) 或类似的东西；如果 c 不能用作表达式，这在某些情况下甚至是不可能的.

Assuming you have used curly braces, as in if (a) { b; }, then you can easily add another step to the body, by writing if (a) { b; c; }. If you had written a && b, then you would need to rewrite this as a && (b, c) or something equivalent; this will not even be possible in some cases, if c cannot function as an expression.

一些 linter 会(合理地)抱怨 a &&b.

Some linters will (reasonably) complain about a && b.

请注意，压缩器通常会将您的第二个示例转换为第一个示例，因此如果您使用 && 的理由是为了节省字节，那么压缩器无论如何都会保存它们.

Note that minifiers will typically convert your second example into the first, so if your rationale for using && is to save bytes, they will be saved anyway by the minifier.

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