哪个更好，数字（x）或parseFloat（x）？ [英] Which is better, number(x) or parseFloat(x)?

问题描述

哪个更好？

我问这只是为了削减几个字节，因为我可以用+ x而不是数字（x）。 parsefloat会做得更好吗？

I'm asking this just for the sake of shaving a few bytes, as I can use +x instead of number(x). Does parsefloat do something better?

推荐答案

parseFloat和Number

之间的区别

parseFloat / parseInt 用于解析字符串，而 Number / + 用于将值强制转换为数字。他们的行为不同。但首先让我们看看它们的行为在哪里：

The difference between parseFloat and Number

parseFloat/parseInt is for parsing a string, while Number/+ is for coercing a value to a number. They behave differently. But first let's look at where they behave the same:

parseFloat('3'); // => 3
Number('3'); // => 3
parseFloat('1.501'); // => 1.501
Number('1.501'); // => 1.501
parseFloat('1e10'); // => 10000000000
Number('1e10'); // => 10000000000

因此，只要你有标准数字输入，就没有区别。但是，如果您的输入以数字开头，然后包含其他字符， parseFloat 会截断字符串中的数字，而数字给出 NaN （不是数字）：

So as long as you have standard numeric input, there's no difference. However, if your input starts with a number and then contains other characters, parseFloat truncates the number out of the string, while Number gives NaN (not a number):

parseFloat('1x'); // => 1
Number('1x'); // => NaN

此外， Number 了解十六进制输入而 parseFloat 不会：

In addition, Number understands hexadecimal input while parseFloat does not:

parseFloat('0x10'); // => 0
Number('0x10'); // => 16

但数字对空字符串的行为很奇怪或仅包含空格的字符串：

But Number acts weird with empty strings or strings containing only white space:

parseFloat(''); // => NaN
Number(''); // => 0
parseFloat(' \r\n\t'); // => NaN
Number(' \r\n\t'); // => 0

总的来说，我发现数字更合理，所以我几乎总是亲自使用 Number （你会发现很多内部JavaScript函数都使用 Number 以及）。如果有人键入'1x'我更喜欢显示错误而不是将其视为输入'1' 。我真正做出异常的唯一一次是当我将样式转换为数字时，在这种情况下 parseFloat 是有用的，因为样式的形式类似于'3px'，在这种情况下，我想放弃'px'部分并获得 3 ，所以我在这里找到 parseFloat 。但是你真正选择哪一个取决于你以及你想接受哪种形式的输入。

On the whole, I find Number to be more reasonable, so I almost always use Number personally (and you'll find that a lot of the internal JavaScript functions use Number as well). If someone types '1x' I prefer to show an error rather than treat it as if they had typed '1'. The only time I really make an exception is when I am converting a style to a number, in which case parseFloat is helpful because styles come in a form like '3px', in which case I want to drop the 'px' part and just get the 3, so I find parseFloat helpful here. But really which one you choose is up to you and which forms of input you want to accept.

注意使用一元 + 运算符与使用 Number 作为函数完全相同：

Note that using the unary + operator is exactly the same as using Number as a function:

Number('0x10'); // => 16
+'0x10'; // => 16
Number('10x'); // => NaN
+'10x'; // => NaN
Number('40'); // => 40
+'40'; // => 40

所以我通常只使用 + 短。只要你知道它的作用，我就会发现它很容易阅读。

So I usually just use + for short. As long as you know what it does, I find it easy to read.

这篇关于哪个更好，数字（x）或parseFloat（x）？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！