调整小数的格式保留小数点后两位

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我是靠谱客的博主称心发带，最近开发中收集的这篇文章主要介绍调整小数的格式保留小数点后两位，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

在开发过程中经常遇到要调整小数的格式，如保留小数点后两位等等。方法也颇为常见，备忘如下。

第一种，利用math.round

var original=28.453
1) //round "original" to two decimals
var result=Math.round(original*100)/100; //returns 28.45
2) // round "original" to 1 decimal
var result=Math.round(original*10)/10; //returns 28.5

第二种，js1.5以上可以利用toFixed(x) ，可指定数字截取小数点后 x位

3) //round "original" to two decimals
var result=original.toFixed(2); //returns 28.45

4) // round "original" to 1 decimal
var result=original.toFixed(1); //returns 28.5

以上两种方法最通用，但却无法满足某些特殊要求，比如保留小数点后两位，如果不满两位，不满两位则补零。此时就有了第三种方法。

第三种，转换函数，这段代码来源于国外一个论坛。

复制代码代码如下:

 
function roundNumber(number,decimals) { 
var newString;// The new rounded number 
decimals = Number(decimals); 
if (decimals < 1) { 
newString = (Math.round(number)).toString(); 
} else { 
var numString = number.toString(); 
if (numString.lastIndexOf(".") == -1) {// If there is no decimal point 
numString += ".";// give it one at the end 
} 
var cutoff = numString.lastIndexOf(".") + decimals;// The point at which to truncate the number 
var d1 = Number(numString.substring(cutoff,cutoff+1));// The value of the last decimal place that we'll end up with 
var d2 = Number(numString.substring(cutoff+1,cutoff+2));// The next decimal, after the last one we want 
if (d2 >= 5) {// Do we need to round up at all? If not, the string will just be truncated 
if (d1 == 9 && cutoff > 0) {// If the last digit is 9, find a new cutoff point 
while (cutoff > 0 && (d1 == 9 || isNaN(d1))) { 
if (d1 != ".") { 
cutoff -= 1; 
d1 = Number(numString.substring(cutoff,cutoff+1)); 
} else { 
cutoff -= 1; 
} 
} 
} 
d1 += 1; 
} 
if (d1 == 10) { 
numString = numString.substring(0, numString.lastIndexOf(".")); 
var roundedNum = Number(numString) + 1; 
newString = roundedNum.toString() + '.'; 
} else { 
newString = numString.substring(0,cutoff) + d1.toString(); 
} 
} 
if (newString.lastIndexOf(".") == -1) {// Do this again, to the new string 
newString += "."; 
} 
var decs = (newString.substring(newString.lastIndexOf(".")+1)).length; 
for(var i=0;i<decimals-decs;i++) newString += "0"; 
//var newNumber = Number(newString);// make it a number if you like 
document.roundform.roundedfield.value = newString; // Output the result to the form field (change for your purposes) 
} 

5) //round "original" to two decimals
var result=original.toFixed(2); //returns 28.45

6) // round "original" to 1 decimal
var result=original.toFixed(1); //returns 28.5

var original=28.4
var result=original.toFixed(2); //returns 28.40