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当我在 JavaScript 中使用指数运算符 (**) 时，它通常按预期工作:
2 ** 2 // 4
2 ** -2 // 0.25
但是当左操作数为负数
-2 ** 2
我收到一个语法错误:
Uncaught SyntaxError: Unexpected token **
我可以通过在 -2 周围加上括号来轻松绕过它
(-2) ** 2 // 4
但我很好奇是什么导致了这个错误。其他运算符(+ - */% 等)没有这个问题。为什么 ** 运算符会发生这种情况？
最佳答案
此行为是有意为之的，目的是防止您编写模棱两可的表达式。 From MDN :
In most languages like PHP and Python and others that have an exponentiation operator (**), the exponentiation operator is defined to have a higher precedence than unary operators such as unary + and unary -, but there are a few exceptions. For example, in Bash the ** operator is defined to have a lower precedence than unary operators. In JavaScript, it is impossible to write an ambiguous exponentiation expression, i.e. you cannot put a unary operator (+/-/~/!/delete/void/typeof) immediately before the base number.
-2 ** 2; // 4 in Bash, -4 in other languages. // This is invalid in JavaScript, as the operation is ambiguous. -(2 ** 2); // -4 in JavaScript and the author's intention is unambiguous.
关于javascript - 为什么求幂运算符的左操作数为负时会出现语法错误？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/52105654/