使用JavaScript获取位数 [英] Get number of digits with JavaScript
问题描述
正如我的帖子的标题建议，我想知道有多少位 var number 。例如：如果 number = 15; 我的函数应该返回 2 。目前，它看起来像这样：
As the title of my post suggests, I would like to know how many digits var number has. For example: If number = 15; my function should return 2. Currently, it looks like this:
function getlength(number) {
return number.toString().length();
}
但Safari说它因为 TypeError ：
But Safari says it is not working due to a TypeError:
'2' is not a function (evaluating 'number.toString().length()')
正如你所看到的，'2'实际上是正确的解决方案。但为什么不是函数？
As you can see, '2' is actually the right solution. But why is it not a function?
推荐答案
length 是一个属性，而不是一个方法。您不能调用它，因此您不需要括号（）：
length is a property, not a method. You can't call it, hence you don't need parenthesis ():
function getlength(number) {
return number.toString().length;
}
UPDATE：上面的例子不能用于浮点数。为了使它工作，我们可以用 String（number）.replace（'。'，''）.length 去掉一个句点，或者用正则表达式： String（number）.match（/ \d / g）.length 。
UPDATE: As discussed in the comments, the above example won't work for float numbers. To make it working we can either get rid of a period with String(number).replace('.', '').length, or count the digits with regular expression: String(number).match(/\d/g).length.
潜在地，获得给定数字中的数字的最快方式是在数学上进行。对于正整数，有一个很好的算法 log10 ：
In terms of speed potentially the fastest way to get number of digits in the given number is to do it mathematically. For positive integers there is a wonderful algorithm with log10:
var length = Math.log(number) * Math.LOG10E + 1 | 0; // for positive integers
对于所有类型的整数（包括负数），有一个辉煌的优化解决方案 @ Mwr247 ，但请谨慎使用 Math.log10 ，因为它不被许多旧版浏览器支持。所以用 Math.log（x）* Math.LOG10E 替换 Math.log10（x） 。
For all types of integers (including negatives) there is a brilliant optimised solution from @Mwr247, but be careful with using Math.log10, as it is not supported by many legacy browsers. So replacing Math.log10(x) with Math.log(x) * Math.LOG10E will solve the compatibility problem.
为创建快速数学解的十进制数字并不容易众所周知的浮点数学行为，所以铸造到字符串的方法将更容易和愚蠢的证明。如 @streetlogics 所述，快速投射可以使用简单的数字到字符串连接，导致 replace 解决方案转换为：
Creating fast mathematical solutions for decimal numbers won't be easy due to well known behaviour of floating point math, so cast-to-string approach will be more easy and fool proof. As mentioned by @streetlogics fast casting can be done with simple number to string concatenation, leading the replace solution to be transformed to:
var length = (number + '').replace('.', '').length; // for floats
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