updated JavaScript function for displaying currency (allows rounding up to next whole cent or dollar)

icur.js

// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/ceil
// https://stackoverflow.com/questions/42109818/reliable-js-rounding-numbers-with-tofixed2-of-a-3-decimal-number
// Closure
(function() {
    /**
     * Decimal adjustment of a number.
     *
     * @param {String}  type  The type of adjustment.
     * @param {Number}  value The number.
     * @param {Integer} exp   The exponent (the 10 logarithm of the adjustment base).
     * @returns {Number} The adjusted value.
     */
    function decimalAdjust(type, value, exp) {
        // If the exp is undefined or zero...
        if (typeof exp === 'undefined' || +exp === 0) {
        return Math[type](value);
        }
        value = +value;
        exp = +exp;
        // If the value is not a number or the exp is not an integer...
        if (isNaN(value) || !(typeof exp === 'number' && exp % 1 === 0)) {
        return NaN;
        }
        // Shift
        value = value.toString().split('e');
        value = Math[type](+(value[0] + 'e' + (value[1] ? (+value[1] - exp) : -exp)));
        // Shift back
        value = value.toString().split('e');
        return +(value[0] + 'e' + (value[1] ? (+value[1] + exp) : exp));
    }

    // Decimal round
    if (!Math.round10) {
        Math.round10 = function(value, exp) {
        return decimalAdjust('round', value, exp);
        };
    }
    // Decimal floor
    if (!Math.floor10) {
        Math.floor10 = function(value, exp) {
        return decimalAdjust('floor', value, exp);
        };
    }
    // Decimal ceil
    if (!Math.ceil10) {
        Math.ceil10 = function(value, exp) {
        return decimalAdjust('ceil', value, exp);
        };
    }
    })();

console.log( icur(1000.021) );
console.log( icur(1000.021, "c") );
console.log( icur(1000.021, "d") );
console.log( icur(1000.021, "cu") );
console.log( icur(1000.021, "du") );
console.log( icur(1000.021, "duc") );
console.log( icur(1000.021, "ducu") );


function icur(a,b){
    // arguments: a=the number  b=the formatting option
    // c (default) 1000.021 > $1,000.02
    // d (dollar only) 1000.021 > $1,000
    // cu (cents rounded up to the next whole cent) 1000.021 > $1,000.03
    // du (dollars rounded up the next whole dollar - no cents) 1000.021 > $1,001
    // duc (dollars rounded up the next whole dollar - with cents) 1000.021 > $1,001.00
    // ducu (dollars rounded up the next whole dollar after cents rounded up to next whole cent - with cents) 1000.021 > $1,001.00


    let displayCents = true;
    let roundCentsUp = false;
    let roundDollarsUp = false;

    if (typeof b === 'undefined') { // argument b is missing (or someone passed b declared as undefined)
        let formatter = new Intl.NumberFormat('en-US', {
            style: 'currency', currency: 'USD',
            minimumFractionDigits: 2 });
        a = formatter.format(a); // 1000.021 => $1,000.02 
        return a;
    }
    else{ // argument b received

        // c (default) 1000.021 > $1,000.02
        if (b === "c"){
            let formatter = new Intl.NumberFormat('en-US', {
                style: 'currency', currency: 'USD',
                minimumFractionDigits: 2 });
            a = formatter.format(a); // 1000.021 => $1,000.02 
            return a;
        }

        // d (dollar only) 1000.021 > $1,000
        if (b === "d"){
            let formatter = new Intl.NumberFormat('en-US', {
                style: 'currency', currency: 'USD',
                minimumFractionDigits: 0, maximumFractionDigits: 0 });
            a = formatter.format(a); // 1000.021 => $1,000.00
            return a;
        }

        // cu (cents rounded up to the next whole cent) 1000.021 > $1,000.03
        if (b === "cu"){
            a = Math.ceil10(a, -2); // the crucial cent up rounding
            let formatter = new Intl.NumberFormat('en-US', {
                style: 'currency', currency: 'USD',
                minimumFractionDigits: 2 });
            a = formatter.format(a); // 1000.021 => $1,000.03
            return a;
        }

        // du (dollars rounded up the next whole dollar - no cents) 1000.021 > $1,001
        if (b === "du"){
            a = Math.ceil10(a, 0); // the crucial dollar up rounding
            let formatter = new Intl.NumberFormat('en-US', {
                style: 'currency', currency: 'USD',
                minimumFractionDigits: 0, maximumFractionDigits: 0 });
            a = formatter.format(a); // 1000.021 => $1,001
            return a;
        }

        // duc (dollars rounded up the next whole dollar - with cents) 1000.021 > $1,001.00
        if (b === "duc"){
            a = Math.ceil10(a, 0); // the crucial dollar up rounding
            let formatter = new Intl.NumberFormat('en-US', {
                style: 'currency', currency: 'USD',
                minimumFractionDigits: 2 });
            a = formatter.format(a); // 1000.021 => $1,001.00
            return a;
        }

        // ducu (dollars rounded up the next whole dollar after cents are rounded up the next whole cent) 1000.021 > $1,001.00
        if (b === "ducu"){
            a = Math.ceil10(a, -2); // the crucial cent up rounding
            a = Math.ceil10(a, 0); // the crucial dollar up rounding
            let formatter = new Intl.NumberFormat('en-US', {
                style: 'currency', currency: 'USD',
                minimumFractionDigits: 2 });
            a = formatter.format(a); // 1000.021 => $1,001.00
            return a;
        }


    }

    return "invalid formatting argument";

}// end icur(a,b)