Number Format In Javascript

Number.toFixed() : 

                               Formats any number for "x" number of trailing decimals. The number is rounded up, and "0"s are used after the decimal point if needed to create the desired decimal length.

 

var profits=2489.8237

profits.toFixed(3) //returns 2489.824 (round up)

profits.toFixed(2) //returns 2489.82

profits.toFixed(7) //returns 2489.8237000 (padding)

 

Number.toPrecision() :

                                  Formats any number so it is of "x" length. Also called significant digits. A decimal point and "0"s are used if needed to create the desired length.

 var anumber=123.45

anumber.toPrecision(6) //returns 123.450 (padding)

anumber.toPrecision(4) //returns 123.5 (round up)

anumber.toPrecision(2) //returns 1.2e+2 (you figure it out!)

Round to a certain number of places

For rounding decimals you can use the built-in JavaScript methods toFixed or toPrecision. 

var num = 10;
var result = num.toFixed(2); // result will equal 10.00

num = 930.9805;
result = num.toFixed(3); // result will equal 930.981

num = 500.2349;
result = num.toPrecision(4); // result will equal 500.2

num = 5000.2349;
result = num.toPrecision(4); // result will equal 5000

num = 555.55;
result = num.toPrecision(2); // result will equal 5.6e+2

Add commas

 

function addCommas(nStr)
{
 nStr += '';
 x = nStr.split('.');
 x1 = x[0];
 x2 = x.length > 1 ? '.' + x[1] : '';
 var rgx = /(\d+)(\d{3})/;
 while (rgx.test(x1)) {
  x1 = x1.replace(rgx, '$1' + ',' + '$2');
 }
 return x1 + x2;
}

Examples

addCommas(1000) // 1,000
addCommas(1231.897243) // 1,231.897243
addCommas('9999999.00') // 9,999,999.00
addCommas(-500000.99) // -500,000.99