# quantity-views > Library for view/set a quantity in several units Latest version **1.1.3** (published 2016-11-15) · MIT license · 0 weekly downloads ## Install ```sh npm install quantity-views pnpm add quantity-views yarn add quantity-views bun add quantity-views ``` ## Health **Score 15/100 (F)** — status: abandoned. Positive: no vulnerabilities. Warnings: low downloads; no types; no esm support. Negative: abandoned; low maintenance score. ## Facts | | | |---|---| | Version | 1.1.3 | | Published | 2016-11-15 | | First published | 2016-11-05 | | Weekly downloads | 0 | | License | MIT | | TypeScript types | none | | Module format | CommonJS | | Node | >=6.8.1 | | Dependencies | 0 | | Known vulnerabilities | 0 | | Install scripts | no | | GitHub stars | 0 | | Author | J Miguel Farto | | Maintainers | damahou | | Keywords | quantity, quantities, units, unit, conversion | ## Links - npm: https://www.npmjs.com/package/quantity-views - Repository: https://github.com/damahou/quantity-views - Homepage: https://github.com/damahou/quantity-views#readme - Issues: https://github.com/damahou/quantity-views/issues - npm.io page: https://npm.io/package/quantity-views ## Recent versions - 1.1.3 (latest) — 2016-11-15 - 1.1.2 — 2016-11-15 - 1.1.1 — 2016-11-15 - 1.1.0 — 2016-11-15 - 1.0.0 — 2016-11-05 ## README # Multi-unit Quantity Views [![License](https://img.shields.io/badge/license-MIT-green.svg)](https://github.com/damahou/quantity-views/blob/master/LICENSE) This is a node library to easily change the displayed unit of a quantity (Length, Area, Speed, Pressure...), and easily set the quantity value in any predefined unit. **Caution:** This library should not be used in code requiring high accuracy or efficient/massive unit conversions. It is intended as an auxiliary resource to implement user interfaces, mainly associated to data binding techniques as in angular or react. ## Installation To install the library, run: $ npm install quantity-views -g or add it as a dependency to your project. ## Basic usage Install the library and try it in a interactive node session $ node First, require one of the builtin quantity classes (more about builtin quantities below) > Length = require('quantity-views').Length [Function: Length] and instanciate it as an object representing for example a width, with a value of 1 (1 what? More below) > width = new Length(value=1, name='width') Length { _value: 1, name: 'width', precision: 15, unit: 'metre' } Check the available units that `width` can display/be set > width.units [ 'metre', 'centimetre', 'millimetre', 'inch', 'foot', 'footUS', 'yard', 'kilometre', 'nauticalMille', 'mille', 'milleUS' ] Obtain our `width` in metres (we discover that the initial values is in metres) > width.metre '1.00000000000000' and then in centimetres > width.centimetre '100.000000000000' Now set our `width` in centimetres > width.centimetre = 3.4 3.4 and get it in metres > width.metre '0.0340000000000000' or inches > width.inch '1.33858267716535' Set `width` as one inch > width.inch = 1 1 and obtain it in millimetres > width.millimetre '25.4000000000000' Inputs can be strings strictly representing floats > width.foot = '2.3' '2.3' > width.metre '0.701040000000000' Weird strings are allowed > width.yard = '34hhjp' '34hhjp' but the quantity then is Not a Number > width.metre 'NaN' Show symbols for every unit > Array.from(width.units, v => [v, width.getSymbol(v)]) [ [ 'metre', 'm' ], [ 'centimetre', 'cm' ], [ 'millimetre', 'mm' ], [ 'inch', 'in' ], [ 'foot', 'ft' ], [ 'footUS', 'ftUS' ], [ 'yard', 'yd' ], [ 'kilometre', 'km' ], [ 'nauticalMille', 'NM' ], [ 'mille', 'mi' ], [ 'milleUS', 'miUS' ] ] ## Builtin quantities The quantity classes available on `require(quantity-views)`, are - Length - Area - Volume - Speed - Acceleration - Mass - Density - Force - Pressure - Torque - Energy - Power - Time - Temperature - DynamicViscosity - KineticViscosity - Adimensional Their constructors can take the optional arguments - `value` A number. Defaults to `NaN`. This is stored in the `this.value` property, provided that `unit` (see below) is one of the valid quantity units listed in `this.units`. In other case, `this._value` is set to NaN. For the builtin quantity classes, `this._value` attribute coincides with the value of the quantity in the corresponding SI base unit (the first unit in `this.units`). - `name` A string. Defaults to `''`. Stored in the `this.name` attribute. Not used by the library. It is an user field. - `precision` A number within 1 and 21 or `null`. Defaults to 15. Stored in the `this.precision` attribute. If `.precision` is a number, all unit queries are strings formatted with 'Number.prototype.toPrecision(quantity.precision)'. If precision is `null`, raw numbers are returned: $ node > Length = require('quantity-views').Length [Function: Length] > distance = new Length() Length { _value: NaN, name: '', precision: 15, unit: 'metre' } > distance.nauticalMille = 2 2 > distance.kilometre '3.70400000000000' > distance.precision = 5 5 > distance.kilometre '3.7040' > distance.mille '2.3016' > distance.precision = null null > distance.kilometre 3.704 > distance.mille 2.301558896047085 > distance.kilometre = '' '' > distance.mille NaN > distance.precision = 10 10 > distance.mille 'NaN' - `unit` A string or `null`. Defaults to `null`. If it is `null` and `this.units` is set, `this.unit` is set to `this.units[0]`, else `this.unit` takes this value. `this.unit` has a side effect in `this.value`: $ node > Length = require('quantity-views').Length [Function: Length] > distance = new Length(3) Length { _value: 3, name: '', precision: 15, unit: 'metre' } > distance.units [ 'metre', 'centimetre', 'millimetre', 'inch', 'foot', 'footUS', 'yard', 'kilometre', 'nauticalMille', 'mille', 'milleUS' ] > distance.unit 'metre' The `value` property returns metres: > distance.value '3.00000000000000' Now, if `unit` property is set to inches, the `value` property returns inches: > distance.unit = 'inch' 'inch' > distance.value '118.110236220472' And setting `value` property is the same as if `inches` property were set > distance.value = 100 100 > distance.metre '2.54000000000000' > distance.inch '100.000000000000' > distance.value '100.000000000000' If a invalid value for `unit` is established, `value` returns `undefined, > distance.unit = 'foo' 'foo' > distance.value undefined and subsequent assignments to the `value`property are ignored: > distance.value = 1 1 > distance.inch '100.000000000000' ## User defined quantities Builtin quantity classes are described in [lib/defs.js](https://github.com/damahou/quantity-views/blob/master/lib/defs.js). Feel free of defining your own quantity classes in the same format. The class `Quantity` is also exported when requiring `quantity-views`. It is a constructor for new quantity classes: $ node Quantity = require('quantity-views').Quantity > MyQties = Quantity.createFromDefs({ ... mylength: [ ... {name: 'astronomicalUnit', multiplier: 1/149597870700, symbol: 'AU'}, ... {name: 'lightSecond', multiplier: 1/299792458, symbol: ''}, ... {name: 'parsec', multiplier: 1/3.085677581e16, symbol: 'pc'}]}) { Mylength: [Function: Mylength] } > coriolanusOdometre = new MyQties.Mylength(66) Mylength { _value: 9873459466200, name: '', precision: 15, unit: 'astronomicalUnit' } > coriolanusOdometre.astronomicalUnit '66.0000000000000' > coriolanusOdometre.lightSecond '32934.3157331863' > coriolanusOdometre.parsec '0.000319977029583247' > coriolanusOdometre._value 9873459466200 Note also that in this example the `._value` is not stored in any unit of the quantity. ## Changelog - v 1.1.3: Mass units fixed. - v 1.1.2: Density symbols fixed. - v 1.1.1: Density symbols fixed. - v 1.1.0: `unit` and `value` properties added. - v 1.0.0: Initial version ## License This code is subject to [MIT](https://github.com/damahou/quantity-views/blob/master/LICENSE) license. --- _Source: https://npm.io/package/quantity-views · Machine-readable twin of the npm.io package page. 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