調整小數(shù)的格式保留小數(shù)點后兩位

更新時間：2014年05月14日 17:20:17 作者：

調整小數(shù)的格式，如保留小數(shù)點后兩位等等在開發(fā)過程中經(jīng)常會遇到，下面本文搜集了一些不錯的實現(xiàn)方法與分享

在開發(fā)過程中經(jīng)常遇到要調整小數(shù)的格式，如保留小數(shù)點后兩位等等。方法也頗為常見，備忘如下。

第一種，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

第二種，js1.5以上可以利用toFixed(x) ，可指定數(shù)字截取小數(shù)點后 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

以上兩種方法最通用，但卻無法滿足某些特殊要求，比如保留小數(shù)點后兩位，如果不滿兩位，不滿兩位則補零。此時就有了第三種方法。

第三種，轉換函數(shù)，這段代碼來源于國外一個論壇。

復制代碼代碼如下:

 
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