Javascript：语句和表达式的区别？ [英] Javascript: difference between a statement and an expression?

问题描述

我问过这个问题在更早的思考之后，我开始怀疑术语表达和表达的含义之间似乎模糊的界限。所有的声明都是表达式？ REPL控制台中的返回值来自哪里？他们并不总是表现出直观的意义。当然，如果您输入 1 + 1 ，您将获得 2 ，但其他时候并不是那么明显什么是逻辑。

I asked this question earlier, and after thinking about the topic some more, I began to wonder where the seemingly fuzzy boundary between the meanings of the terms "statement" and "expression" lies. Are all statements also expressions? Where do the return values in a REPL console come from? They don't always seem to make any intuitive sense. Of course if you type 1+1, you'll get 2, but other times it isn't as obvious what the logic is.

鉴于键入到REPL的任何内容都会产生一些值，这是否意味着可以在JS源代码中使用一个表达式和一个独立的语句？

Given that anything typed into REPL produces some value, does it mean that it can be used in JS source code as both an expression and a standalone statement?

可以在以下代码段中使用可用于 _X _ 的代码字符串也可以用于 _Y _ ，反之亦然 if（_X_）_Y _

can string of code that could be used for _X_ in the following snippet also be used for _Y_ and vice versa? if(_X_) _Y_

推荐答案

所有语句是否都是表达式？

Are all statements also expressions?

JavaScript可以在哪里查询一个语句，还可以写一个表达式。这样的语句称为表达式语句。反之亦然：您无法编写JavaScript期望表达式的语句。例如，if语句不能成为函数的参数。

"Wherever JavaScript expects a statement, you can also write an expression. Such a statement is called an expression statement. The reverse does not hold: you cannot write a statement where JavaScript expects an expression. For example, an if statement cannot become the argument of a function."

这是来自Axel Rauschmayer最近发表的关于这个主题的文章：
表达式与JavaScript中的语句

This is comes from a recent post by Axel Rauschmayer about this topic: Expressions versus statements in JavaScript

希望它有帮助。

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