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Santhosh Kumar
Santhosh Kumar

Posted on • Edited on

fcal - Math expression evaluator in Javascript

#javascript #typescript #npm #node

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Fcaljs is an extensive math expression evaluator library for JavaScript and Node.js.
Using fcal, you can perform basic arithmetic, percentage operations with precision.
It features a flexible expression parser with a large set of built-in units, functions and constants.
Inspired from Numi

Features

  • Units
  • Variables
  • Functions

Playground Codepen , CLI

Example 

const fcal = new Fcal(); // New variable fcal.evaluate('radius : 23 m'); // 23 Meters fcal.evaluate('PI * radius ^ 2'); // 1661.9025137490006231 Meters fcal.evaluate('PI2 * radius'); // 144.51326206514 Meters // Predefined functions fcal.evaluate('log(23)'); // 1.3617278360175928789 // Percentage fcal.evaluate('23 % of 1023'); // 235.29 fcal.evaluate('200 sec + 120 %'); // 440 Seconds // Unit conversion fcal.evaluate('20 minutes + 34 day in sec'); // 2938800 Seconds fcal.evaluate('sin(PI)'); // -1.6167204971158028306e-24 // Constants fcal.evaluate('E'); // 2.718281828459045235360287 // Predefined units fcal.evaluate('speed = 20 kph'); // 20 km/h fcal.evaluate('speed in mps'); // 5.5555555555555555556 m/s fcal.evaluate('23 C add 123 F'); // 196.40000000000004 °F fcal.evaluate('1.2 nsec + 3 week in sec'); // 1814400.0000000012 Seconds // Various number system fcal.evaluate('0b1010011 day + 45'); // 128 Days fcal.evaluate('23.44 kmh in oct'); // 0o27.341217270243656051 km/h
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Install

Browser

the library is the single JavaScript file fcal.js (or minified, fcal.min.js).

<script src="https://cdn.jsdelivr.net/npm/fcal/dist/fcal.js"></script>
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With NPM 

$ npm install --save fcal
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const { Fcal } = require('fcal');
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Use 

const { Fcal } = require('fcal'); const fcal = new Fcal(); var value = fcal.evaluate('102 day in minutes + abs(-34 day) in sec'); console.log(value); // 11750400 Seconds
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Percentage 

var value = fcal.evaluate('27% of 230 cm'); console.log(value); // 62.1 Centimeters
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You can perform general percentage operation with + , -

var value = fcal.evaluate('1024 m + 6.1%'); console.log(value); // 1086.464 Meters
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If type of left and right hand side of of is same, then operation will return percentage

var value = fcal.evaluate('10 of 10.100'); console.log(value); // % 99.009900990099009901
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Scales

You can use Thousand k, million M and billion B scales.

var value = Fcal.eval('-0x14 M'); console.log(value); //-20000000
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Equality and comparison 

console.log(Fcal.eval('100 == 1230')); // false console.log(Fcal.eval('20 cm < 1 m')); // true console.log(Fcal.eval('100 cm != 100 m')); // true
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You can use === to compare irrespective type of value

console.log(Fcal.eval('100 C === 100 F')); // true
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Ternary operator 

var value = Fcal.eval('234 cm > 1 m and true ? 34: 100'); console.log(value); // 34
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Syntax errors

Fcal will throw exception if there is error with expression

For more error context, use info method in FcalError

try { var value = Fcal.eval('343 + 23.45E+*34'); } catch (e) { if (e instanceof FcalError) { console.log(e.info()); } } /* err: Expecting number after + but got '*' | 343 + 23.45E+*34 | ......^^^^^^^ */
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Strict mode

By default, fcal will not throw exception if you try to use operations between different types or different units

But with strict mode

const fcal = new Fcal(); fcal.setStrict(true) try { var value = fcal.evaluate('23% + 34 cm + 1'); } catch (e) { if (e instanceof FcalError) { console.log(e.info()); } /* err: Unexpected '+' operation between different types (unit, number) | 23% + 34 cm + 1 | ^^^^^^^^^^^^^^^ */
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Using expression

You can change state of expression , re evaluate it

const { Fcal } = require('fcal'); const exp = new Fcal().expression('PI * radius cm ^ 2'); exp.setValues({ radius: 8 }); console.log(exp.evaluate()); // 201.06192982974676726 Centimeters exp.setValues({ radius: 10 }); console.log(exp.evaluate()); // 314.15926535897932385 Centimeters exp.setValues({ radius: Infinity }); console.log(exp.evaluate()); // Infinity Centimeters
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🤝 Contributing

Contributions, issues and feature requests are welcome!
Feel free to check issues page.

To contribute

$ git clone https://github.com/5anthosh/fcal
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$ npm install
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Run tests 

$ npm test
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