[javascript] Format numbers in JavaScript similar to C#

Is there a simple way to format numbers in JavaScript, similar to the formatting methods available in C# (or VB.NET) via ToString("format_provider") or String.Format()?

This question is related to javascript jquery format numbers

The answer is


Generally

In jQuery


To get a decimal with 2 numbers after the comma, you could just use:

function nformat(a) {
   var b = parseInt(parseFloat(a)*100)/100;
   return b.toFixed(2);
}

I made a simple function, maybe someone can use it

function secsToTime(secs){
  function format(number){
    if(number===0){
      return '00';
    }else {
      if (number < 10) {
          return '0' + number
      } else{
          return ''+number;
      }
    }
  }

  var minutes = Math.floor(secs/60)%60;
  var hours = Math.floor(secs/(60*60))%24;
  var days = Math.floor(secs/(60*60*24));
  var seconds = Math.floor(secs)%60;

  return (days>0? days+"d " : "")+format(hours)+':'+format(minutes)+':'+format(seconds);
}

this can generate the followings outputs:

  • 5d 02:53:39
  • 4d 22:15:16
  • 03:01:05
  • 00:00:00

Here's another version:

$.fn.digits = function () {
    return this.each(function () {
        var value = $(this).text();
        var decimal = "";
        if (value) {
            var pos = value.indexOf(".");
            if (pos >= 0) {
                decimal = value.substring(pos);
                value = value.substring(0, pos);
            }
            if (value) {
                value = value.replace(/(\d)(?=(\d\d\d)+(?!\d))/g, "$1,");
                if (!String.isNullOrEmpty(decimal)) value = (value + decimal);
                $(this).text(value);
            }
        }
        else {
            value = $(this).val()
            if (value) {
                var pos = value.indexOf(".");
                if (pos >= 0) {
                    decimal = value.substring(pos);
                    value = value.substring(0, pos);
                }
                if (value) {
                    value = value.replace(/(\d)(?=(\d\d\d)+(?!\d))/g, "$1,");
                    if (!String.isNullOrEmpty(decimal)) value = (value + decimal);
                    $(this).val(value);
                }
            }
        }
    })
};

I wrote a simple function (not yet another jQuery plugin needed!!) that converts a number to a decimal separated string or an empty string if the number wasn't a number to begin with:

function format(x) {
    return isNaN(x)?"":x.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
}

format(578999); results in 578,999

format(10); results in 10

if you want to have a decimal point instead of a comma simply replace the comma in the code with a decimal point.

One of the comments correctly stated this only works for integers, with a few small adaptions you can make it work for floating points as well:

function format(x) {
    if(isNaN(x))return "";

    n= x.toString().split('.');
    return n[0].replace(/\B(?=(\d{3})+(?!\d))/g, ",")+(n.length>1?"."+n[1]:"");
}

Firstly, converting an integer into string in JS is really simple:

// Start off with a number
var number = 42;
// Convert into a string by appending an empty (or whatever you like as a string) to it
var string = 42+'';
// No extra conversion is needed, even though you could actually do
var alsoString = number.toString();

If you have a number as a string and want it to be turned to an integer, you have to use the parseInt(string) for integers and parseFloat(string) for floats. Both of these functions then return the desired integer/float. Example:

// Start off with a float as a string
var stringFloat = '3.14';
// And an int as a string
var stringInt = '42';

// typeof stringInt  would give you 'string'

// Get the real float from the string
var realFloat = parseFloat(someFloat);
// Same for the int
var realInt = parseInt(stringInt);

// but typeof realInt  will now give you 'number'

What exactly are you trying to append etc, remains unclear to me from your question.


Here are some solutions, all pass the test suite, test suite and benchmark included, if you want copy and paste to test, try This Gist.

Method 0 (RegExp)

Base on https://stackoverflow.com/a/14428340/1877620, but fix if there is no decimal point.

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('.');
    }
}

Method 1

if (typeof Number.prototype.format1 === 'undefined') {
    Number.prototype.format1 = 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('.');
    };
}

Method 2 (Split to Array)

if (typeof Number.prototype.format2 === 'undefined') {
    Number.prototype.format2 = 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('.');
    };
}

Method 3 (Loop)

if (typeof Number.prototype.format3 === 'undefined') {
    Number.prototype.format3 = 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('');
    };
}

Example

console.log('======== Demo ========')
var n = 0;
for (var i=1; i<20; i++) {
    n = (n * 10) + (i % 10)/100;
    console.log(n.format(2), (-n).format(2));
}

Separator

If we want custom thousands separator or decimal separator, use replace():

123456.78.format(2).replace(',', ' ').replace('.', ' ');

Test suite

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);

Benchmark

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');
}

async = [];
function next() {
    setTimeout(function () {
        f = async.shift();
        f && f();
        next();
    }, 10);
}

console.log('======== Benchmark ========');
async.push(function () { benchmark_format(Number.prototype.format); });
async.push(function () { benchmark_format(Number.prototype.format1); });
async.push(function () { benchmark_format(Number.prototype.format2); });
async.push(function () { benchmark_format(Number.prototype.format3); });
next();

To further jfriend00's answer (I dont't have enough points to comment) I have extended his/her answer to the following:

_x000D_
_x000D_
function log(args) {_x000D_
    var str = "";_x000D_
    for (var i = 0; i < arguments.length; i++) {_x000D_
        if (typeof arguments[i] === "object") {_x000D_
            str += JSON.stringify(arguments[i]);_x000D_
        } else {_x000D_
            str += arguments[i];_x000D_
        }_x000D_
    }_x000D_
    var div = document.createElement("div");_x000D_
    div.innerHTML = str;_x000D_
    document.body.appendChild(div);_x000D_
}_x000D_
_x000D_
Number.prototype.addCommas = function (str) {_x000D_
    if (str === undefined) {_x000D_
     str = this;_x000D_
    }_x000D_
    _x000D_
    var parts = (str + "").split("."),_x000D_
        main = parts[0],_x000D_
        len = main.length,_x000D_
        output = "",_x000D_
        first = main.charAt(0),_x000D_
        i;_x000D_
    _x000D_
    if (first === '-') {_x000D_
        main = main.slice(1);_x000D_
        len = main.length;    _x000D_
    } else {_x000D_
       first = "";_x000D_
    }_x000D_
    i = len - 1;_x000D_
    while(i >= 0) {_x000D_
        output = main.charAt(i) + output;_x000D_
        if ((len - i) % 3 === 0 && i > 0) {_x000D_
            output = "," + output;_x000D_
        }_x000D_
        --i;_x000D_
    }_x000D_
    // put sign back_x000D_
    output = first + output;_x000D_
    // put decimal part back_x000D_
    if (parts.length > 1) {_x000D_
        output += "." + parts[1];_x000D_
    }_x000D_
    return output;_x000D_
}_x000D_
_x000D_
var testCases = [_x000D_
    1, 12, 123, -1234, 12345, 123456, -1234567, 12345678, 123456789,_x000D_
    -1.1, 12.1, 123.1, 1234.1, -12345.1, -123456.1, -1234567.1, 12345678.1, 123456789.1_x000D_
];_x000D_
 _x000D_
for (var i = 0; i < testCases.length; i++) {_x000D_
 log(testCases[i].addCommas());_x000D_
}_x000D_
 _x000D_
/*for (var i = 0; i < testCases.length; i++) {_x000D_
    log(Number.addCommas(testCases[i]));_x000D_
}*/
_x000D_
_x000D_
_x000D_


Yes, there is definitely a way to format numbers properly in javascript, for example:

var val=2489.8237

val.toFixed(3) //returns 2489.824 (round up)
val.toFixed(2) //returns 2489.82
val.toFixed(7) //returns 2489.8237000 (padding)

With the use of variablename.toFixed .

And there is another function toPrecision() . For more detail you also can visit

http://raovishal.blogspot.com/2012/01/number-format-in-javascript.html


You can do it in the following way: So you will not only format the number but you can also pass as a parameter how many decimal digits to display, you set a custom decimal and mile separator.

function format(number, decimals = 2, decimalSeparator = '.', thousandsSeparator = ',') {
    const roundedNumber = number.toFixed(decimals);
    let integerPart = '', fractionalPart = '';
    if (decimals == 0) {
        integerPart = roundedNumber;
        decimalSeparator = '';
    } else {
        let numberParts = roundedNumber.split('.');
        integerPart = numberParts[0];
        fractionalPart = numberParts[1];
    }
    integerPart = integerPart.replace(/(\d)(?=(\d{3})+(?!\d))/g, `$1${thousandsSeparator}`);
    return `${integerPart}${decimalSeparator}${fractionalPart}`;
}

Use:

let min = 1556454.0001;
let max = 15556982.9999;
console.time('number format');
for (let i = 0; i < 15000; i++) {
    let randomNumber = Math.random() * (max - min) + min;

    let formated = format(randomNumber, 4, ',', '.'); // formated number

    console.debug('number: ', randomNumber, 'formated: ', formated);
}
console.timeEnd('number format');

Using JQuery.

$(document).ready(function()
 {
    //Only number and one dot
    function onlyDecimal(element, decimals)
    {
        $(element).keypress(function(event)
        {
            num = $(this).val() ;
            num = isNaN(num) || num === '' || num === null ? 0.00 : num ;
            if ((event.which != 46 || $(this).val().indexOf('.') != -1) && (event.which < 48 || event.which > 57))
            {
                event.preventDefault();

            }
            if($(this).val() == parseFloat(num).toFixed(decimals))
            {
                event.preventDefault();
            }
        });
    }

     onlyDecimal("#TextBox1", 3) ;



});


If you don't want to use jQuery, take a look at Numeral.js


In case you want to format number for view rather than for calculation you can use this

function numberFormat( number ){

    var digitCount = (number+"").length;
    var formatedNumber = number+"";
    var ind = digitCount%3 || 3;
    var temparr = formatedNumber.split('');

    if( digitCount > 3 && digitCount <= 6 ){

        temparr.splice(ind,0,',');
        formatedNumber = temparr.join('');

    }else if (digitCount >= 7 && digitCount <= 15) {
        var temparr2 = temparr.slice(0, ind);
        temparr2.push(',');
        temparr2.push(temparr[ind]);
        temparr2.push(temparr[ind + 1]);
        // temparr2.push( temparr[ind + 2] ); 
        if (digitCount >= 7 && digitCount <= 9) {
            temparr2.push(" million");
        } else if (digitCount >= 10 && digitCount <= 12) {
            temparr2.push(" billion");
        } else if (digitCount >= 13 && digitCount <= 15) {
            temparr2.push(" trillion");

        }
        formatedNumber = temparr2.join('');
    }
    return formatedNumber;
}

Input: {Integer} Number

Outputs: {String} Number

22,870 => if number 22870

22,87 million => if number 2287xxxx (x can be whatever)

22,87 billion => if number 2287xxxxxxx

22,87 trillion => if number 2287xxxxxxxxxx

You get the idea


http://code.google.com/p/javascript-number-formatter/ :

  • Short, fast, flexible yet standalone. Only 75 lines including MIT license info, blank lines & comments.
  • Accept standard number formatting like #,##0.00 or with negation -000.####.
  • Accept any country format like # ##0,00, #,###.##, #'###.## or any type of non-numbering symbol.
  • Accept any numbers of digit grouping. #,##,#0.000 or #,###0.## are all valid.
  • Accept any redundant/fool-proof formatting. ##,###,##.# or 0#,#00#.###0# are all OK.
  • Auto number rounding.
  • Simple interface, just supply mask & value like this: format( "0.0000", 3.141592)

UPDATE

As say Tomáš Zato here one line solution:

(666.0).toLocaleString()
numObj.toLocaleString([locales [, options]])

which described in ECMA-262 5.1 Edition:

and will work in future versions of browsers...


Here's a simple JS function to add commas to an integer number in string format. It will handle whole numbers or decimal numbers. You can pass it either a number or a string. It obviously returns a string.

function addCommas(str) {
    var parts = (str + "").split("."),
        main = parts[0],
        len = main.length,
        output = "",
        first = main.charAt(0),
        i;

    if (first === '-') {
        main = main.slice(1);
        len = main.length;    
    } else {
        first = "";
    }
    i = len - 1;
    while(i >= 0) {
        output = main.charAt(i) + output;
        if ((len - i) % 3 === 0 && i > 0) {
            output = "," + output;
        }
        --i;
    }
    // put sign back
    output = first + output;
    // put decimal part back
    if (parts.length > 1) {
        output += "." + parts[1];
    }
    return output;
}

Here's a set of test cases: http://jsfiddle.net/jfriend00/6y57j/

You can see it being used in this previous jsFiddle: http://jsfiddle.net/jfriend00/sMnjT/. You can find functions that will handle decimal numbers too with a simple Google search for "javascript add commas".

Converting a number to a string can be done many ways. The easiest is just to add it to a string:

var myNumber = 3;
var myStr = "" + myNumber;   // "3"

Within, the context of your jsFiddle, you'd get commas into the counter by changing this line:

jTarget.text(current);

to this:

jTarget.text(addCommas(current));

You can see it working here: http://jsfiddle.net/jfriend00/CbjSX/


May I suggest numbro for locale based formatting and number-format.js for the general case. A combination of the two depending on use-case may help.


For example:

var flt = '5.99';
var nt = '6';

var rflt = parseFloat(flt);
var rnt = parseInt(nt);

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