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

问题描述

哪个更好?

我问这个只是为了减少几个字节，因为我可以使用 +x 而不是 number(x).parsefloat 是否做得更好?

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 的区别

parseFloat/parseInt 用于解析字符串，而 Number/+ 用于将值强制转换为一个号码.他们的行为不同.但首先让我们看看它们的行为相同的地方:

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

所以只要您有标准的数字输入，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 Number 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

另外，Number 理解十六进制输入而 parseFloat 不理解:

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

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

但是 Number 对于空字符串或只包含空格的字符串表现得很奇怪:

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

parseFloat(''); // => NaN
Number(''); // => 0
parseFloat(' 
	'); // => NaN
Number(' 
	'); // => 0

总的来说，我觉得Number更合理，所以我个人几乎总是使用Number(你会发现很多内部JavaScript函数也使用 Number).如果有人输入 '1x'，我更愿意显示错误，而不是将其视为他们输入了 '1'.我唯一真正的例外是当我将样式转换为数字时，在这种情况下 parseFloat 很有帮助，因为样式以 '3px' 之类的形式出现，在这种情况下，我想删除 'px' 部分而只获取 3，所以我发现 parseFloat 在这里很有帮助.但实际上，您选择哪一种取决于您以及您希望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.

请注意，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 + 简称.只要你知道它的作用，我觉得它很容易阅读.

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

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