javascript 未捕获的语法错误：意外的令牌返回 - 仍然没有答案？
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Uncaught SyntaxError: Unexpected token return - still no answer?
提问by Dmitri Zaitsev
So there are dozens of questions with this title, however, all answers I could find seem to mention some hacks working in some specific cases but not being helpful in others. Many are concerned with jQuery or Ajax, yet the problem is pure JavaScript arising at very basic level:
所以这个标题有很多问题，但是，我能找到的所有答案似乎都提到了一些在某些特定情况下有效但在其他情况下没有帮助的技巧。许多人关注 jQuery 或 Ajax，但问题是在非常基础的层面上出现的纯 JavaScript：
function f() {
false || (return true);
}
This function declaration (without execution) throws
这个函数声明（不执行）抛出
Uncaught SyntaxError: Unexpected token return
Uncaught SyntaxError: Unexpected token return
in Chrome and
在 Chrome 和
SyntaxError: Return statements are only valid inside functions
SyntaxError: Return statements are only valid inside functions
in Safari. However this function doesn't:
在 Safari 中。但是，此功能不会：
function f() {
false || (a=true);
return true;
}
Anybody can explain this strange behaviour?
任何人都可以解释这种奇怪的行为吗？
采纳答案by elclanrs
Because returnis not an expression, but it expectsan expression:
因为return不是一个表达式，但它需要一个表达式：
function f() {
return false || true;
}
回答by thefourtheye
You are using returnstatement in an expression, as an expression, which is not possible as JavaScript engine cannot evaluate it. Thats why it is throwing the error.
您return在表达式中使用语句作为表达式，这是不可能的，因为 JavaScript 引擎无法评估它。这就是它抛出错误的原因。
