我想用JavaScript格式化价格。我想要一个函数，它将浮点作为参数，并返回如下格式的字符串：
"$ 2,500.00"
我该怎么做？
当前回答
Numeral.js-一个JavaScript库，通过@adamwdraper轻松设置数字格式
numeral(23456.789).format('$0,0.00'); // = "$23,456.79"
其他回答
YUI代码库使用以下格式：
format: function(nData, oConfig) {
oConfig = oConfig || {};
if(!YAHOO.lang.isNumber(nData)) {
nData *= 1;
}
if(YAHOO.lang.isNumber(nData)) {
var sOutput = nData + "";
var sDecimalSeparator = (oConfig.decimalSeparator) ? oConfig.decimalSeparator : ".";
var nDotIndex;
// Manage decimals
if(YAHOO.lang.isNumber(oConfig.decimalPlaces)) {
// Round to the correct decimal place
var nDecimalPlaces = oConfig.decimalPlaces;
var nDecimal = Math.pow(10, nDecimalPlaces);
sOutput = Math.round(nData*nDecimal)/nDecimal + "";
nDotIndex = sOutput.lastIndexOf(".");
if(nDecimalPlaces > 0) {
// Add the decimal separator
if(nDotIndex < 0) {
sOutput += sDecimalSeparator;
nDotIndex = sOutput.length-1;
}
// Replace the "."
else if(sDecimalSeparator !== "."){
sOutput = sOutput.replace(".",sDecimalSeparator);
}
// Add missing zeros
while((sOutput.length - 1 - nDotIndex) < nDecimalPlaces) {
sOutput += "0";
}
}
}
// Add the thousands separator
if(oConfig.thousandsSeparator) {
var sThousandsSeparator = oConfig.thousandsSeparator;
nDotIndex = sOutput.lastIndexOf(sDecimalSeparator);
nDotIndex = (nDotIndex > -1) ? nDotIndex : sOutput.length;
var sNewOutput = sOutput.substring(nDotIndex);
var nCount = -1;
for (var i=nDotIndex; i>0; i--) {
nCount++;
if ((nCount%3 === 0) && (i !== nDotIndex)) {
sNewOutput = sThousandsSeparator + sNewOutput;
}
sNewOutput = sOutput.charAt(i-1) + sNewOutput;
}
sOutput = sNewOutput;
}
// Prepend prefix
sOutput = (oConfig.prefix) ? oConfig.prefix + sOutput : sOutput;
// Append suffix
sOutput = (oConfig.suffix) ? sOutput + oConfig.suffix : sOutput;
return sOutput;
}
// Still not a number. Just return it unaltered
else {
return nData;
}
}
它需要编辑，因为YUI库是可配置的，比如用“.”替换oConfig.decimalSeparator。
JavaScript中没有“formatNumber”的等价物。你可以自己写，也可以找一个已经这样做的库。
PHP函数“number_format”有一个JavaScript端口。
我发现它非常有用，因为它易于使用，并且对PHP开发人员来说是可识别的。
function number_format (number, decimals, dec_point, thousands_sep) {
var n = number, prec = decimals;
var toFixedFix = function (n,prec) {
var k = Math.pow(10,prec);
return (Math.round(n*k)/k).toString();
};
n = !isFinite(+n) ? 0 : +n;
prec = !isFinite(+prec) ? 0 : Math.abs(prec);
var sep = (typeof thousands_sep === 'undefined') ? ',' : thousands_sep;
var dec = (typeof dec_point === 'undefined') ? '.' : dec_point;
var s = (prec > 0) ? toFixedFix(n, prec) : toFixedFix(Math.round(n), prec);
// Fix for Internet Explorer parseFloat(0.55).toFixed(0) = 0;
var abs = toFixedFix(Math.abs(n), prec);
var _, i;
if (abs >= 1000) {
_ = abs.split(/\D/);
i = _[0].length % 3 || 3;
_[0] = s.slice(0,i + (n < 0)) +
_[0].slice(i).replace(/(\d{3})/g, sep+'$1');
s = _.join(dec);
} else {
s = s.replace('.', dec);
}
var decPos = s.indexOf(dec);
if (prec >= 1 && decPos !== -1 && (s.length-decPos-1) < prec) {
s += new Array(prec-(s.length-decPos-1)).join(0)+'0';
}
else if (prec >= 1 && decPos === -1) {
s += dec+new Array(prec).join(0)+'0';
}
return s;
}
（原文注释栏，包括以下示例和到期信用）
// Formats a number with grouped thousands
//
// version: 906.1806
// discuss at: http://phpjs.org/functions/number_format
// + original by: Jonas Raoni Soares Silva (http://www.jsfromhell.com)
// + improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
// + bugfix by: Michael White (http://getsprink.com)
// + bugfix by: Benjamin Lupton
// + bugfix by: Allan Jensen (http://www.winternet.no)
// + revised by: Jonas Raoni Soares Silva (http://www.jsfromhell.com)
// + bugfix by: Howard Yeend
// + revised by: Luke Smith (http://lucassmith.name)
// + bugfix by: Diogo Resende
// + bugfix by: Rival
// + input by: Kheang Hok Chin (http://www.distantia.ca/)
// + improved by: davook
// + improved by: Brett Zamir (http://brett-zamir.me)
// + input by: Jay Klehr
// + improved by: Brett Zamir (http://brett-zamir.me)
// + input by: Amir Habibi (http://www.residence-mixte.com/)
// + bugfix by: Brett Zamir (http://brett-zamir.me)
// * example 1: number_format(1234.56);
// * returns 1: '1,235'
// * example 2: number_format(1234.56, 2, ',', ' ');
// * returns 2: '1 234,56'
// * example 3: number_format(1234.5678, 2, '.', '');
// * returns 3: '1234.57'
// * example 4: number_format(67, 2, ',', '.');
// * returns 4: '67,00'
// * example 5: number_format(1000);
// * returns 5: '1,000'
// * example 6: number_format(67.311, 2);
// * returns 6: '67.31'
// * example 7: number_format(1000.55, 1);
// * returns 7: '1,000.6'
// * example 8: number_format(67000, 5, ',', '.');
// * returns 8: '67.000,00000'
// * example 9: number_format(0.9, 0);
// * returns 9: '1'
// * example 10: number_format('1.20', 2);
// * returns 10: '1.20'
// * example 11: number_format('1.20', 4);
// * returns 11: '1.2000'
// * example 12: number_format('1.2000', 3);
// * returns 12: '1.200'
这里有一些解决方案，都通过了测试套件。包括测试套件和基准测试。如果你想复制和粘贴来测试，试试这个要点。
方法0（RegExp）
它是基于VisioN的答案，但如果没有小数点，它会修复。
if (typeof Number.prototype.format === 'undefined') {
Number.prototype.format = function (precision) {
if (!isFinite(this)) {
return this.toString();
}
var a = this.toFixed(precision).split('.');
a[0] = a[0].replace(/\d(?=(\d{3})+$)/g, '$&,');
return a.join('.');
}
}
方法1
if (typeof Number.prototype.format === 'undefined') {
Number.prototype.format = function (precision) {
if (!isFinite(this)) {
return this.toString();
}
var a = this.toFixed(precision).split('.'),
// Skip the '-' sign
head = Number(this < 0);
// Skip the digits that's before the first thousands separator
head += (a[0].length - head) % 3 || 3;
a[0] = a[0].slice(0, head) + a[0].slice(head).replace(/\d{3}/g, ',$&');
return a.join('.');
};
}
方法2（拆分到阵列）
if (typeof Number.prototype.format === 'undefined') {
Number.prototype.format = function (precision) {
if (!isFinite(this)) {
return this.toString();
}
var a = this.toFixed(precision).split('.');
a[0] = a[0]
.split('').reverse().join('')
.replace(/\d{3}(?=\d)/g, '$&,')
.split('').reverse().join('');
return a.join('.');
};
}
方法3（循环）
if (typeof Number.prototype.format === 'undefined') {
Number.prototype.format = function (precision) {
if (!isFinite(this)) {
return this.toString();
}
var a = this.toFixed(precision).split('');
a.push('.');
var i = a.indexOf('.') - 3;
while (i > 0 && a[i-1] !== '-') {
a.splice(i, 0, ',');
i -= 3;
}
a.pop();
return a.join('');
};
}
用法示例
console.log('======== Demo ========')
console.log(
(1234567).format(0),
(1234.56).format(2),
(-1234.56).format(0)
);
var n = 0;
for (var i=1; i<20; i++) {
n = (n * 10) + (i % 10)/100;
console.log(n.format(2), (-n).format(2));
}
分离器
如果我们需要自定义千位分隔符或小数分隔符，请使用replace（）：
123456.78.format(2).replace(',', ' ').replace('.', ' ');
测试套件
function assertEqual(a, b) {
if (a !== b) {
throw a + ' !== ' + b;
}
}
function test(format_function) {
console.log(format_function);
assertEqual('NaN', format_function.call(NaN, 0))
assertEqual('Infinity', format_function.call(Infinity, 0))
assertEqual('-Infinity', format_function.call(-Infinity, 0))
assertEqual('0', format_function.call(0, 0))
assertEqual('0.00', format_function.call(0, 2))
assertEqual('1', format_function.call(1, 0))
assertEqual('-1', format_function.call(-1, 0))
// Decimal padding
assertEqual('1.00', format_function.call(1, 2))
assertEqual('-1.00', format_function.call(-1, 2))
// Decimal rounding
assertEqual('0.12', format_function.call(0.123456, 2))
assertEqual('0.1235', format_function.call(0.123456, 4))
assertEqual('-0.12', format_function.call(-0.123456, 2))
assertEqual('-0.1235', format_function.call(-0.123456, 4))
// Thousands separator
assertEqual('1,234', format_function.call(1234.123456, 0))
assertEqual('12,345', format_function.call(12345.123456, 0))
assertEqual('123,456', format_function.call(123456.123456, 0))
assertEqual('1,234,567', format_function.call(1234567.123456, 0))
assertEqual('12,345,678', format_function.call(12345678.123456, 0))
assertEqual('123,456,789', format_function.call(123456789.123456, 0))
assertEqual('-1,234', format_function.call(-1234.123456, 0))
assertEqual('-12,345', format_function.call(-12345.123456, 0))
assertEqual('-123,456', format_function.call(-123456.123456, 0))
assertEqual('-1,234,567', format_function.call(-1234567.123456, 0))
assertEqual('-12,345,678', format_function.call(-12345678.123456, 0))
assertEqual('-123,456,789', format_function.call(-123456789.123456, 0))
// Thousands separator and decimal
assertEqual('1,234.12', format_function.call(1234.123456, 2))
assertEqual('12,345.12', format_function.call(12345.123456, 2))
assertEqual('123,456.12', format_function.call(123456.123456, 2))
assertEqual('1,234,567.12', format_function.call(1234567.123456, 2))
assertEqual('12,345,678.12', format_function.call(12345678.123456, 2))
assertEqual('123,456,789.12', format_function.call(123456789.123456, 2))
assertEqual('-1,234.12', format_function.call(-1234.123456, 2))
assertEqual('-12,345.12', format_function.call(-12345.123456, 2))
assertEqual('-123,456.12', format_function.call(-123456.123456, 2))
assertEqual('-1,234,567.12', format_function.call(-1234567.123456, 2))
assertEqual('-12,345,678.12', format_function.call(-12345678.123456, 2))
assertEqual('-123,456,789.12', format_function.call(-123456789.123456, 2))
}
console.log('======== Testing ========');
test(Number.prototype.format);
test(Number.prototype.format1);
test(Number.prototype.format2);
test(Number.prototype.format3);
基准
function benchmark(f) {
var start = new Date().getTime();
f();
return new Date().getTime() - start;
}
function benchmark_format(f) {
console.log(f);
time = benchmark(function () {
for (var i = 0; i < 100000; i++) {
f.call(123456789, 0);
f.call(123456789, 2);
}
});
console.log(time.format(0) + 'ms');
}
// If not using async, the browser will stop responding while running.
// This will create a new thread to benchmark
async = [];
function next() {
setTimeout(function () {
f = async.shift();
f && f();
next();
}, 10);
}
console.log('======== Benchmark ========');
async.push(function () { benchmark_format(Number.prototype.format); });
next();
这是另一个尝试，只是为了好玩：
function formatDollar(num) {
var p = num.toFixed(2).split(".");
return "$" + p[0].split("").reverse().reduce(function(acc, num, i, orig) {
return num + (num != "-" && i && !(i % 3) ? "," : "") + acc;
}, "") + "." + p[1];
}
还有一些测试：
formatDollar(45664544.23423) // "$45,664,544.23"
formatDollar(45) // "$45.00"
formatDollar(123) // "$123.00"
formatDollar(7824) // "$7,824.00"
formatDollar(1) // "$1.00"
formatDollar(-1345) // "$-1,345.00
formatDollar(-3) // "$-3.00"
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