Utilities to convert between various byte capacities

capacity.js

/**
 * Represents a capacity in bytes.
 * @class
 * @param {Number} sizeInBytes - The size in bytes.
 * @prop {Number} oneKB - One kilobyte.
 * @prop {Number} oneMB - One megabyte.
 * @prop {Number} oneGB - One gigabyte.
 * @prop {Number} oneTB - One terabyte.
 */
function Capacity(sizeInBytes) {
    if (!(this instanceof Capacity)) return new Capacity(sizeInBytes);

    if (sizeInBytes === undefined || isNaN(sizeInBytes)) {
        throw new Error("Required argument undefined: 'sizeInBytes'");
    }

    if (sizeInBytes < 0) {
        throw new Error("Invalid size specified: 'sizeInBytes'");
    }

    Object.defineProperty(this, 'sizeInBytes', { value: sizeInBytes });
}

Object.defineProperty(Capacity, 'oneKB', { value: 1024 });
Object.defineProperty(Capacity, 'oneMB', { value: 1024 * 1024 });
Object.defineProperty(Capacity, 'oneGB', { value: 1024 * 1024 * 1024 });
Object.defineProperty(Capacity, 'oneTB', { value: 1024 * 1024 * 1024 * 1024 });

/** @func
 * @name toBytes
 * @returns {Number} - The size in bytes.
 */
Capacity.prototype.toBytes = function toBytes() {
    return this.sizeInBytes;
}

/** @func
 * @name toKB
 * @returns {Number} - The size in kilobytes.
 */
Capacity.prototype.toKB = function toKB() {
    return this.sizeInBytes / Capacity.oneKB;
}

/** @func
 * @name toMB
 * @returns {Number} - The size in megabytes.
 */
Capacity.prototype.toMB = function toMB() {
    return this.sizeInBytes / Capacity.oneMB;
}

/** @func
 * @name toGB
 * @returns {Number} - The size in gigabytes.
 */
Capacity.prototype.toGB = function toGB() {
    return this.sizeInBytes / Capacity.oneGB;
}

/** @func
 * @name toTB
 * @returns {Number} - The size in terabytes.
*/
Capacity.prototype.toTB = function toTB() {
    return this.sizeInBytes / Capacity.oneTB;
}

/** @func toKBString */
Capacity.prototype.toKBString = function toKBString(precision) {
    return this.toKB().toFixed(precision) + ' KB';
}

/** @func toMBString */
Capacity.prototype.toMBString = function toMBString(precision) {
    return this.toMB().toFixed(precision) + ' MB';
}

/** @func toGBString */
Capacity.prototype.toGBString = function toGBString(precision) {
    return this.toGB().toFixed(precision) + ' GB';
}

/** @func toTBString */
Capacity.prototype.toTBString = function toTBString(precision) {
    return this.toTB().toFixed(precision) + ' TB';
}

/** @func toNearestByteString */
Capacity.prototype.toNearestByteString = function toNearestByteString(precision) {
    if (this.sizeInBytes < Capacity.oneMB) {
        return this.toKBString(precision);
    }

    if (this.sizeInBytes < Capacity.oneGB) {
        return this.toMBString(precision);
    }

    if (this.sizeInBytes < Capacity.oneTB) {
        return this.toGBString(precision);
    }

    return this.toTBString(precision);
}

Capacity.prototype.toString = function capacityToString() {
    return this.sizeInBytes.toString();
}

if (module && module.exports) {
    module.exports.Capacity = Capacity;
}