javascript 数字保留数字后面小数点

看到很多人有这保留数字后面小数点的需求但是大多数是自己写一个函数来截取还要考虑四捨五入啥的写起来还挺复杂的

其实javascript的Number对象是有一个保留小数点后面的小数的方法的toFixed它是四捨五入后的数

我一度担心IE不支持这个方法看到MDN里面说这个方法是javascript才出来专门在IE下试了下是完全支持

toExponential([fractionDigits])  将数字按科学计数法格式返回其中的fractionDigits值小数点后保留的位数

toFixed([fractionDigits]) 将数字按指定的小数点位数返回其中的fractionDigits值小数点后保留的位数

toPrecision([precision])  将数字按指定的精度返回(这个精度不是指小数点后几位)其中precision是指定的精度值

例子如下

代码如下

var n = ;

ntoFixed(); // Returns

ntoFixed(); // Returns

ntoFixed(); // Returns

(e+)toFixed(); // Returns

(e)toFixed(); // Returns

toFixed(); // Returns

toFixed(); // Returns

()toFixed(); // Returns

转换函数这段代码来源于国外一个论坛

代码如下

function roundNumber(numberdecimals) {

var newString;// The new rounded number

decimals = Number(decimals);

if (decimals < ) {

newString = (Mathround(number))toString();

} else {

var numString = numbertoString();

if (numStringlastIndexOf("") == ) {// If there is no decimal point

numString += "";// give it one at the end

}

var cutoff = numStringlastIndexOf("") + decimals;// The point at which to  truncate the number

var d = Number(numStringsubstring(cutoffcutoff+));// The value of the  last decimal place that well end up with

var d = Number(numStringsubstring(cutoff+cutoff+));// The next  decimal after the last one we want

if (d >= ) {// Do we need to round up at all? If not the string will  just be truncated

if (d == && cutoff > ) {// If the last digit is find a  new cutoff point

while (cutoff > && (d == || isNaN(d))) {

if (d != "") {

cutoff = ;

d = Number(numStringsubstring(cutoffcutoff+));

} else {

cutoff = ;

}

}

}

d += ;

}

if (d == ) {

numString = numStringsubstring( numStringlastIndexOf(""));

var roundedNum = Number(numString) + ;

newString = roundedNumtoString() + ;

} else {

newString = numStringsubstring(cutoff) + dtoString();

}

}

if (newStringlastIndexOf("") == ) {// Do this again to the new  string

newString += "";

}

var decs = (newStringsubstring(newStringlastIndexOf("")+))length;

for(var i=;i

//var newNumber = Number(newString);// make it a number if you like

documentroundformroundedfieldvalue = newString; // Output the result to  the form field (change for your purposes)

}