luzlab/meteor-quantities

FATHOM:Quantities

This packages add support to Meteor for using numbers with phyiscal units. This package Meteor-izes the js-quantities npm module, adding the necessary methods to support serialization and deserialization by Meteor. This allows the use of quanties in publications, Meteor methods and arguments.

Example usage

import Qty from 'meteor/fathom:quantities';

if (Meteor.isServer) {
    Meteor.methods({
      'is_10cm': function is_10cm(qty) {
            let ten_cm = Qty('10 cm');
            let result = qty.eq(ten_cm);
            return result;
        }
    );
}

let qty2 = Qty('0.1 m');
Meteor.call('is_10cm', qty2) // returns true

let weight = Qty('1.1 g');
let volume = Qty('1 cm^3');
let density = weight.div(volume);

let sample_volume = Qty('0.1 m^3');
let sample_weight = sample_volume.add(density); // returns QtyError 'Incompatible units'
let sample_weight = sample_volume.div(density); // Note - we should multiple, not divide, by density
sample_weight.toString('kg'); // returns QtyError 'Incompatible units' since we dividied by density...

let sample_weight = sample_volume.mul(density); // Do the right operation with density
sample_weight.toString('kg'); // returns '110 g' // Now these work as expected
sample_weight.toString('lb'); // returns the '242.50848840336533 lb'
sample_weight.toString('lb', 2); // returns the '242.51 lb'
sample_weight.toString('m'); // returns QtyError 'Incompatible units'

This package uses the npm module ejson-extras to registers a custom EJSON type for Qty objects. In addition, this package extends Qty.prototype to provide readable output when logging. Altogether, the Qty.prototype is extended with the following methods:

• .typeName() - returns 'js-quantity'
• .toJSONValue() - returns a JSON-ifyable string
• .clone() - Returns a new Qty object equal to the argument.
• .equals() - defers to Qty.eq() method if units are compatible; false otherwise
• .inspect() - returns human-readable representation of the Qty (eg. "12.1 m") instead of dumping the internal JSON representation.

Changelog

1.0.6 Updated ejson-extras module to fix Map stringify/parse bug

1.0.5 Added missing test dependancies