books/utils/number_format.js

const number_formats = {
    "#,###.##": { fraction_sep: ".", group_sep: ",", precision: 2 },
    "#.###,##": { fraction_sep: ",", group_sep: ".", precision: 2 },
    "# ###.##": { fraction_sep: ".", group_sep: " ", precision: 2 },
    "# ###,##": { fraction_sep: ",", group_sep: " ", precision: 2 },
    "#'###.##": { fraction_sep: ".", group_sep: "'", precision: 2 },
    "#, ###.##": { fraction_sep: ".", group_sep: ", ", precision: 2 },
    "#,##,###.##": { fraction_sep: ".", group_sep: ",", precision: 2 },
    "#,###.###": { fraction_sep: ".", group_sep: ",", precision: 3 },
    "#.###": { fraction_sep: "", group_sep: ".", precision: 0 },
    "#,###": { fraction_sep: "", group_sep: ",", precision: 0 },
}

module.exports = {
    // parse a formatted number string
    // from "4,555,000.34" -> 4555000.34
    parse_number(number, format='#,###.##') {
        if (!number) {
            return 0;
        }
        if (typeof number === 'number') {
            return number;
        }
        const info = this.get_format_info(format);
        return parseFloat(this.remove_separator(number, info.group_sep));
    },

    format_number(number, format = '#,###.##', precision = null) {
        if (!number) {
            number = 0;
        }
        let info = this.get_format_info(format);
        if (precision) {
            info.precision = precision;
        }
        let is_negative = false;

        number = this.parse_number(number);
        if (number < 0) {
            is_negative = true;
        }
        number = Math.abs(number);
        number = number.toFixed(info.precision);

        var parts = number.split('.');

        // get group position and parts
        var group_position = info.group_sep ? 3 : 0;

        if (group_position) {
            var integer = parts[0];
            var str = '';
            var offset = integer.length % group_position;
            for (var i = integer.length; i >= 0; i--) {
                var l = this.remove_separator(str, info.group_sep).length;
                if (format == "#,##,###.##" && str.indexOf(",") != -1) { // INR
                    group_position = 2;
                    l += 1;
                }

                str += integer.charAt(i);

                if (l && !((l + 1) % group_position) && i != 0) {
                    str += info.group_sep;
                }
            }
            parts[0] = str.split("").reverse().join("");
        }
        if (parts[0] + "" == "") {
            parts[0] = "0";
        }

        // join decimal
        parts[1] = (parts[1] && info.fraction_sep) ? (info.fraction_sep + parts[1]) : "";

        // join
        return (is_negative ? "-" : "") + parts[0] + parts[1];
    },

    get_format_info(format) {
        let format_info = number_formats[format];

        if (!format_info) {
            throw `Unknown number format "${format}"`;
        }

        return format_info;
    },

    round(num, precision) {
        var is_negative = num < 0 ? true : false;
        var d = parseInt(precision || 0);
        var m = Math.pow(10, d);
        var n = +(d ? Math.abs(num) * m : Math.abs(num)).toFixed(8); // Avoid rounding errors
        var i = Math.floor(n), f = n - i;
        var r = ((!precision && f == 0.5) ? ((i % 2 == 0) ? i : i + 1) : Math.round(n));
        r = d ? r / m : r;
        return is_negative ? -r : r;
    },

    remove_separator(text, sep) {
        return text.replace(new RegExp(sep === "." ? "\\." : sep, "g"), '');
    }
};