JavaScript中的小数点分隔符号是什么？ [英] What is the decimal separator symbol in JavaScript?

问题描述

当我编写一段处理一些浮点值的JavaScript代码时，一个想法让我感到震惊。 JavaScript中的小数点符号是什么？它总是。？还是文化特有的？那么 .toFixed（）和 .parseFloat（）呢？如果我正在处理用户输入，则可能包含本地文化特定的小数点分隔符号。

A thought struck me as I was writing a piece of JavaScript code that processed some floating point values. What is the decimal point symbol in JavaScript? Is it always .? Or is it culture-specific? And what about .toFixed() and .parseFloat()? If I'm processing a user input, it's likely to include the local culture-specific decimal separator symbol.

最终我想编写支持两个小数点的代码在用户输入中 - 特定于文化和。，但如果我不知道JavaScript期望什么，我就无法编写这样的代码。

Ultimately I'd like to write code that supports both decimal points in user input - culture-specific and ., but I can't write such a code if I don't know what JavaScript expects.

已添加：好的，Rubens Farias 建议查看类似的问题，它有一个很好的接受答案：

Added: OK, Rubens Farias suggests to look at similar question which has a neat accepted answer:

function whatDecimalSeparator() {
    var n = 1.1;
    n = n.toLocaleString().substring(1, 2);
   return n;
}

这很好，它让我得到区域设置小数点。毫无疑问，迈向解决方案的一步。

That's nice, it lets me get the locale decimal point. A step towards the solution, no doubt.

现在，剩下的部分将是确定 .parseFloat（）是。几个答案指出，对于浮点文字，只有。有效。 .parseFloat（）的行为方式是否相同？或者它可能在某些浏览器中需要本地小数点分隔符？是否有任何不同的方法来解析浮点数？我应该推出自己的应该吗？

Now, the remaining part would be to determine what the behavior of .parseFloat() is. Several answers point out that for floating point literals only . is valid. Does .parseFloat() act the same way? Or might it require the local decimal separator in some browser? Are there any different methods for parsing floating point numbers as well? Should I roll out my own just-to-be-sure?

推荐答案

根据规范，DecimalLiteral定义为：

According to the specification, a DecimalLiteral is defined as:

DecimalLiteral ::
    DecimalIntegerLiteral . DecimalDigitsopt ExponentPartopt 
    . DecimalDigits ExponentPartopt 
    DecimalIntegerLiteral ExponentPartopt

以及满足parseFloat参数：

and for satisfying the parseFloat argument:

1. 让inputString为ToString（string）。


2. 让trimmedString成为inputString的子串，由最左边的字符组成一个StrWhiteSpaceChar和该角色右边的所有字符。（换句话说，删除前导空格。）


3. 如果trimmedString和trimmedString的任何前缀都不满足StrDecimalLiteral的语法（请参阅9.3.1），返回NaN。


4. 让numberString成为trimmedString的最长前缀，它可能是trimmedString本身，它满足StrDecimalLiteral的语法。


5. 返回MV的Number值

1. Let inputString be ToString(string).
2. Let trimmedString be a substring of inputString consisting of the leftmost character that is not a StrWhiteSpaceChar and all characters to the right of that character.(In other words, remove leading white space.)
3. If neither trimmedString nor any prefix of trimmedString satisfies the syntax of a StrDecimalLiteral (see 9.3.1), return NaN.
4. Let numberString be the longest prefix of trimmedString, which might be trimmedString itself, that satisfies the syntax of a StrDecimalLiteral.
5. Return the Number value for the MV

因此numberString成为trimmedString的最长前缀，满足StrDecimalLiteral的语法，意思是它找到的第一个可解析的文字字符串数字输入。只能使用。来指定浮点数。如果您接受来自不同语言环境的输入，请使用字符串替换：

So numberString becomes the longest prefix of trimmedString that satisfies the syntax of a StrDecimalLiteral, meaning the first parseable literal string number it finds in the input. Only the . can be used to specify a floating-point number. If you're accepting inputs from different locales, use a string replace:

function parseLocalNum(num) {
    return +(num.replace(",", "."));
}

该函数使用一元运算符而不是parseFloat，因为在我看来你是想要严格的输入。 parseFloat（1ABC）将是 1 ，而使用一元运算符 +1ABC 返回 NaN 。这使得验证输入变得更加容易。使用parseFloat只是猜测输入格式正确。

The function uses the unary operator instead of parseFloat because it seems to me that you want to be strict about the input. parseFloat("1ABC") would be 1, whereas using the unary operator +"1ABC" returns NaN. This makes it MUCH easier to validate the input. Using parseFloat is just guessing that the input is in the correct format.

这篇关于JavaScript中的小数点分隔符号是什么？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！