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    2.1.1 • Public • Published


    Originally a fork of gentooboontoo/js-quantities rewritten in typescript.

    Installing ts-quantities


    Install it in your project

    npm install --save ts-quantities

    Import it !

    import { Qty } from 'ts-quantities'

    Using ts-quantities


    ts-quantities heavily relies on Qty objects. To create Qty objects, use its constructor using new.

    qty = new Qty('23 ft');

    Qty constructor accepts strings, numbers and Qty instances as initializing values.

    If scalars and their respective units are available programmatically, the two argument signature may be useful:

    qty = new Qty(124, 'cm'); // => 1.24 meter
    qty = new Qty('1m'); // => 1 meter
    qty = new Qty('m'); // =>  1 meter (scalar defaults to 1)
    qty = new Qty('1 N*m');
    qty = new Qty('1 N m'); // * is optional
    qty = new Qty('1 m/s');
    qty = new Qty('1 m^2/s^2');
    qty = new Qty('1 m^2 s^-2'); // negative powers
    qty = new Qty('1 m2 s-2'); // ^ is optional
    qty = new Qty('1 m^2 kg^2 J^2/s^2 A');
    qty = new Qty('1.5'); // unitless quantity
    qty = new Qty(1.5); // number as initializing value
    qty = new Qty('1 attoparsec/microfortnight');
    qtyCopy = new Qty(qty); // quantity could be copied when used as
                            // initializing value

    Parsing a quantity manually

    Qty.parse utility method is also provided to parse and create quantities from strings. Unlike the constructor, it will return null instead of throwing an error when parsing an invalid quantity.

    static parse(valuestring)Qty
    Qty.parse('1 m'); // => 1 meter
    Qty.parse('foo'); // => null

    Available well-known kinds

    static getKinds()string[]
    Qty.getKinds(); // => Array of names of every well-known kind of units

    Available units of a particular kind

    static getUnits(kind?: string)string[]
    Qty.getUnits('currency'); // => [ 'dollar', 'cents' ]
    Qty.getUnits(); // All units, alphebetically sorted => [ 'acre','Ah','ampere','AMU','angstrom', ...]

    Alternative names of a unit

    static getAliases(unitNamestring)string[]
    Qty.getAliases('m'); // => [ 'm', 'meter', 'meters', 'metre', 'metres' ]

    Quantity compatibility, kind and various queries

    public isCompatible(otherQty | string)boolean
    qty1.isCompatible(qty2); // => true or false
    public kind()string
    qty.kind(); // => 'length', 'area', etc...
    public isUnitless()boolean
    qty.isUnitless(); // => true or false
    public isBase()boolean
    qty.isBase(); // => true if quantity is represented with base units


    public toBase()Qty
    qty.toBase(); // converts to SI units (10 cm => 0.1 m) (new instance)
    public toFloat()number
    qty.toFloat(); // returns scalar of unitless quantity
                   // (otherwise throws error)
    public to(Qty | string)Qty
    qty.to('m'); // converts quantity to meter if compatible
                 // or throws an error (new instance)
    qty1.to(qty2); // converts quantity to same unit of qty2 if compatible
                   // or throws an error (new instance)
    public inverse()Qty
    qty.inverse(); // converts quantity to its inverse
                   // ('100 m/s' => '0.01 s/m')
    // Inverses can be used, but there is no special checking to
    // rename the units
    new Qty('10ohm').inverse(); // '0.1/ohm'
                           // (not '0.1S', although they are equivalent)
    // however, the 'to' command will convert between inverses also
    new Qty('10ohm').to('S'); // '0.1S'
    public convertSingleUnit(baseUnitstring, targetUnitstring)Qty
    // Converts the selected baseUnit into the target unit. Others units remain untouched.
    new Qty('0.14 USD/kWh').convertSingleUnit('kWh', 'MWh'); // 140 USD/MWh
    new Qty('4000 m2').convertSingleUnit('m', 'km'); // 0.004 km2

    Mass conversion

    Qty.swiftConverter() is a fast way to efficiently convert large array of Number values. It configures a function accepting a value or an array of Number values to convert.

    static swiftConverter(srcUnitsstring, dstUnitsstring): (value: number | number[]) => number | number[]
    const convert = Qty.swiftConverter('m/h', 'ft/s'); // Configures converter
    // Converting single value
    const converted = convert(2500); // => 2.278..
    // Converting large array of values
    const convertedArray = convert([2500, 5000, ...]); // => [2.278.., 4.556.., ...]

    The main drawback of this conversion method is that it does not take care of rounding issues.


    public eq(otherQty)boolean
    qty1.eq(qty2); // => true if both quantities are equal (1m == 100cm => true)
    public same(otherQty)boolean
    qty1.same(qty2); // => true if both quantities are same (1m == 100cm => false)
    public lt(otherQty)boolean
    qty1.lt(qty2); // => true if qty1 is stricty less than qty2
    public lte(otherQty)boolean
    qty1.lte(qty2); // => true if qty1 is less than or equal to qty2
    public gt(otherQty)boolean
    qty1.gt(qty2); // => true if qty1 is stricty greater than qty2
    public gte(otherQty)boolean
    qty1.gte(qty2); // => true if qty1 is greater than or equal to qty2
    public compareTo(otherQty)number
    qty1.compareTo(qty2); // => -1 if qty1 < qty2,
                          // => 0 if qty1 == qty2,
                          // => 1 if qty1 > qty2


    public add(otherQty | string | number)Qty // other should be unit compatible.
    public sub(otherQty | string | number)Qty // other should be unit compatible.
    public mul(otherQty | string | number)Qty
    public div(otherQty | string | number)Qty


    Qty#toPrec(precision) : returns the nearest multiple of quantity passed as precision.

    public toPrec(precQuantityQty | string | number)Qty
    const qty = new Qty('5.17 ft');
    qty.toPrec('ft'); // => 5 ft
    qty.toPrec('0.5 ft'); // => 5 ft
    qty.toPrec('0.25 ft'); // => 5.25 ft
    qty.toPrec('0.1 ft'); // => 5.2 ft
    qty.toPrec('0.05 ft'); // => 5.15 ft
    qty.toPrec('0.01 ft'); // => 5.17 ft
    qty.toPrec('0.00001 ft'); // => 5.17 ft
    qty.toPrec('2 ft'); // => 6 ft
    qty.toPrec('2'); // => 6 ft
    const qty = new Qty('6.3782 m');
    qty.toPrec('dm'); // => 6.4 m
    qty.toPrec('cm'); // => 6.38 m
    qty.toPrec('mm'); // => 6.378 m
    qty.toPrec('5 cm'); // => 6.4 m
    qty.toPrec('10 m'); // => 10 m
    qty.toPrec(0.1); // => 6.3 m
    const qty = new Qty('1.146 MPa');
    qty.toPrec('0.1 bar'); // => 1.15 MPa

    Formatting quantities

    Qty#toString returns a string using the canonical form of the quantity (that is it could be seamlessly reparsed by Qty).

    public toString(toUnits?: string)string
    var qty = new Qty('1.146 MPa');
    qty.toString(); // => '1.146 MPa'

    As a shorthand, units could be passed to Qty#toString and is equivalent to successively call Qty#to then Qty#toString.

    const qty = new Qty('1.146 MPa');
    qty.toString('bar'); // => '11.46 bar'
    qty.to('bar').toString(); // => '11.46 bar'

    Qty#toString could also be used with any method from Qty to make some sort of formatting. For instance, one could use Qty#toPrec to fix the maximum number of decimals:

    const qty = new Qty('1.146 MPa');
    qty.toPrec(0.1).toString(); // => '1.1 MPa'
    qty.to('bar').toPrec(0.1).toString(); // => '11.5 bar'

    For advanced formatting needs as localization, specific rounding or any other custom customization, quantities can be transformed into strings through Qty#format according to optional target units and formatter. If target units are specified, the quantity is converted into them before formatting.

    Such a string is not intended to be reparsed to construct a new instance of Qty (unlike output of Qty#toString).

    If no formatter is specified, quantities are formatted according to default ts-quantities' formatter and is equivalent to Qty#toString.

    type Formatter = (scalar: number, units: string) => string;
    public format(formatter?: Formatter)string;
    public format(targetUnits?: string, formatter?: Formatter)string;
    var qty = new Qty('1.1234 m');
    qty.format(); // same units, default formatter => '1.234 m'
    qty.format('cm'); // converted to 'cm', default formatter => '123.45 cm'

    Qty#format could delegates formatting to a custom formatter if required. A formatter is a callback function accepting scalar and units as parameters and returning a formatted string representing the quantity.

    const configurableRoundingFormatter = (maxDecimals: number): Formatter => {
      return (scalar: number, units: string): string => {
        const pow = Math.pow(10, maxDecimals);
        const rounded = Math.round(scalar * pow) / pow;
        return rounded + ' ' + units;
    const qty = new Qty('1.1234 m');
    // same units, custom formatter => '1.12 m'
    // convert to 'cm', custom formatter => '123.4 cm'
    qty.format('cm', configurableRoundingFormatter(1));

    Custom formatter can be configured globally by setting Qty.formatter.

    static formatterFormatter;
    Qty.formatter = configurableRoundingFormatter(2);
    const qty = new Qty('1.1234 m');
    qty.format(); // same units, current default formatter => '1.12 m'


    Like ruby-units, ts-quantities makes a distinction between a temperature (which technically is a property) and degrees of temperature (which temperatures are measured in).

    Temperature units (i.e., 'tempK') can be converted back and forth, and will take into account the differences in the zero points of the various scales. Differential temperature (e.g., '100 degC') units behave like most other units.

    new Qty('37 tempC').to('tempF') // => 98.6 tempF

    ts-quantities will throw an error if you attempt to create a temperature unit that would fall below absolute zero.

    Unit math on temperatures is fairly limited.

    new Qty('100 tempC').add('10 degC')  // 110 tempC
    new Qty('100 tempC').sub('10 degC')  // 90 tempC
    new Qty('100 tempC').add('50 tempC') // throws error
    new Qty('100 tempC').sub('50 tempC') // 50 degC
    new Qty('50 tempC').sub('100 tempC') // -50 degC
    new Qty('100 tempC').mul(scalar)     // 100*scalar tempC
    new Qty('100 tempC').div(scalar)     // 100/scalar tempC
    new Qty('100 tempC').mul(qty)        // throws error
    new Qty('100 tempC').div(qty)        // throws error
    new Qty('100 tempC*unit')            // throws error
    new Qty('100 tempC/unit')            // throws error
    new Qty('100 unit/tempC')            // throws error
    new Qty('100 tempC').inverse()       // throws error
    new Qty('100 tempC').to('degC') // => 100 degC

    This conversion references the 0 point on the scale of the temperature unit

    new Qty('100 degC').to('tempC') // => -173.15 tempC

    These conversions are always interpreted as being relative to absolute zero. Conversions are probably better done like this...

    new Qty('0 tempC').add('100 degC') // => 100 tempC


    Every error thrown by ts-quantities is an instance of Qty.Error.

    try {
      // code triggering an error inside ts-quantities
    catch(error) {
      if(error instanceof Qty.Error) {
        // ...
      else {
        // ...


    Tests are implemented with Jasmine (https://github.com/pivotal/jasmine).

    To execute specs through jasmine-node, launch:

    npm install -g jasmine-node
    npm run test


    Feedback and contributions are welcomed.

    Pull requests must pass tests and linting. Please make sure that npm run test and npm run lint return no errors before submitting.


    npm i ts-quantities

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