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Cover image for fcal -Extensive math expression evaluator library for JavaScript and Node.js

fcal -Extensive math expression evaluator library for JavaScript and Node.js

5anthosh profile image Santhosh Kumar ・3 min read

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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

Fcal gui

Features

  • Units
  • Variables
  • Functions

Playground Fcal GUI, 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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Discussion

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