JavaScript equivalent for PHP number format.

number_format.js

/**
* Format a number with grouped thousands
* 
* @param number The number being formatted
* @param decimals Sets the number of decimal points
* @param dec_point Sets the separator for the decimal point
* @param thousands_sep Sets the thousands separator
* @returns string A formatted version of number
*/
function number_format( number, decimals, dec_point, thousands_sep ) {
    // Strip all characters but numerical ones.
    number = ( number + '' ).replace( /[^0-9+\-Ee.]/g, '' );

    var n = !isFinite( +number ) ? 0 : +number,
        prec = !isFinite( +decimals ) ? 0 : Math.abs( decimals ),
        sep = ( typeof thousands_sep === 'undefined' ) ? ',' : thousands_sep,
        dec = ( typeof dec_point === 'undefined' ) ? '.' : dec_point,
        s = '',
        toFixedFix = function ( n, prec ) {
            var k = Math.pow( 10, prec );
            return '' + ( Math.round( n * k ) / k ).toFixed(prec);
        };
        
    // Fix for IE parseFloat(0.55).toFixed(0) = 0;
    s = ( prec ? toFixedFix( n, prec ) : '' + Math.round( n ) ).split( '.' );

    if ( s[0].length > 3 ) {
        s[0] = s[0].replace( /\B(?=(?:\d{3})+(?!\d))/g, sep );
    }

    if ( ( s[1] || '' ).length < prec ) {
        s[1] = s[1] || '';
        s[1] += new Array( prec - s[1].length + 1 ).join( '0' );
    }

    return s.join( dec );
}