在 JavaScript 中获取数字中小数位数的最简单方法 [英] Simplest way of getting the number of decimals in a number in JavaScript

问题描述

有没有比我的例子更好的方法来计算数字的小数位数?

Is there a better way of figuring out the number of decimals on a number than in my example?

var nbr = 37.435.45;
var decimals = (nbr!=Math.floor(nbr))?(nbr.toString()).split('.')[1].length:0;

更好"是指更快地执行和/或使用原生 JavaScript 函数，即.类似 nbr.getDecimals().

By better I mean faster to execute and/or using a native JavaScript function, ie. something like nbr.getDecimals().

提前致谢！

修改 series0ne 答案后，我能管理的最快方法是:

After modifying series0ne answer, the fastest way I could manage is:

var val = 37.435345;
var countDecimals = function(value) {
    if (Math.floor(value) !== value)
        return value.toString().split(".")[1].length || 0;
    return 0;
}
countDecimals(val);

速度测试:http://jsperf.com/checkdecimals

推荐答案

Number.prototype.countDecimals = function () {
    if(Math.floor(this.valueOf()) === this.valueOf()) return 0;
    return this.toString().split(".")[1].length || 0; 
}

当绑定到原型时，这允许您直接从数字变量中获取十进制计数 (countDecimals();).

When bound to the prototype, this allows you to get the decimal count (countDecimals();) directly from a number variable.

例如

var x = 23.453453453;
x.countDecimals(); // 9

它的工作原理是将数字转换为字符串，在 . 处拆分并返回数组的最后一部分，如果数组的最后一部分未定义，则返回 0(如果存在没有小数点).

It works by converting the number to a string, splitting at the . and returning the last part of the array, or 0 if the last part of the array is undefined (which will occur if there was no decimal point).

如果你不想将 this 绑定到原型，你可以使用 this:

If you do not want to bind this to the prototype, you can just use this:

var countDecimals = function (value) {
    if(Math.floor(value) === value) return 0;
    return value.toString().split(".")[1].length || 0; 
}

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布莱克

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EDIT by Black:

我已经修复了该方法，使其也适用于较小的数字，例如 0.000000001

I have fixed the method, to also make it work with smaller numbers like 0.000000001

Number.prototype.countDecimals = function () {

    if (Math.floor(this.valueOf()) === this.valueOf()) return 0;

    var str = this.toString();
    if (str.indexOf(".") !== -1 && str.indexOf("-") !== -1) {
        return str.split("-")[1] || 0;
    } else if (str.indexOf(".") !== -1) {
        return str.split(".")[1].length || 0;
    }
    return str.split("-")[1] || 0;
}


var x = 23.453453453;
console.log(x.countDecimals()); // 9

var x = 0.0000000001;
console.log(x.countDecimals()); // 10

var x = 0.000000000000270;
console.log(x.countDecimals()); // 13

var x = 101;  // Integer number
console.log(x.countDecimals()); // 0

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