为什么10..toString（）有效，但10.toString（）不起作用？ [英] Why does 10..toString() work, but 10.toString() does not?

问题描述

可能重复：

在JavaScript中使用toString

152..toString(2)

正确创建二进制字符串10011000，但

correctly creates the binary string "10011000", but

152.toString(2)

抛出异常

语法错误：标识符在数字文字后立即启动

"SyntaxError: identifier starts immediately after numeric literal"

为什么？后一种语法实际上听起来更正确，而前者看起来很奇怪！

Why? The latter syntax actually sounds more correct while the former looks very odd!

推荐答案

A 。在一个数字看似含糊不清之后。它是小数还是对象成员运算符？

A . after a number might seem ambiguous. Is it a decimal or an object member operator?

然而，解释器决定它是小数，所以你错过了成员运算符。

However, the interpreter decides that it's a decimal, so you're missing the member operator.

它看起来像这样：

(10.)toString();  // invalid syntax

当你包含第二个时。，你有一个小数后跟成员运算符。

When you include the second ., you have a decimal followed by the member operator.

(10.).toString();

---

@pedants and downvoters

。 字符会出现歧义。可以理解为成员运算符或小数，具体取决于其位置。如果没有歧义，那就毫无疑问。

The . character presents an ambiguity. It can be understood to be the member operator, or a decimal, depending on its placement. If there was no ambiguity, there would be no question to ask.

规范对。字符的解释那个特定的位置是小数点。这是由ECMAScript的数字文字语法定义的。

The specification's interpretation of the . character in that particular position is that it will be a decimal. This is defined by the numeric literal syntax of ECMAScript.

仅仅因为规范解决了JS解释器的歧义，并不意味着<$ c的模糊性$ c>。字符根本不存在。

Just because the specification resolves the ambiguity for the JS interpreter, doesn't mean that the ambiguity of the . character doesn't exist at all.

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