fcal - Math expression evaluator in Javascript
Tags: javascript, typescript, npm, node
Published: 2019-11-07 12:20:24

### 🏠 [Homepage](https://github.com/5anthosh/fcal/wiki)

> 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](https://numi.app)

## Features

- Units
- Variables
- Functions

> Playground [Codepen](https://codepen.io/5anthosh/full/XWWdyMg) , [CLI](https://github.com/5anthosh/fcal-cli)

## Example

```js
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
```

## Install

### Browser

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

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

### With [NPM](https://www.npmjs.com/)

```sh
$ npm install --save fcal
```

```js
const { Fcal } = require('fcal');
```

## Use

```js
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
```

### Percentage

```js
var value = fcal.evaluate('27% of 230 cm');
console.log(value); // 62.1 Centimeters
```

You can perform general percentage operation with `+` , `-`

```js
var value = fcal.evaluate('1024 m + 6.1%');
console.log(value); // 1086.464 Meters
```

If type of left and right hand side of `of` is same, then operation will return percentage

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

### Scales

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

```js
var value = Fcal.eval('-0x14 M');
console.log(value); //-20000000
```

### Equality and comparison

```js
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
```

You can use `===` to compare irrespective type of value

```js
console.log(Fcal.eval('100 C === 100 F')); // true
```

#### Ternary operator

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

### Syntax errors

Fcal will throw exception if there is error with expression

For more error context, use _info_ method in _FcalError_

```js
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
| ......^^^^^^^
*/
```

#### 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

```js
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
| ^^^^^^^^^^^^^^^
*/
```

### Using expression

You can change state of expression , re evaluate it

```js
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
```

## 🤝 Contributing

Contributions, issues and feature requests are welcome!<br />Feel free to check [issues page](https://github.com/5anthosh/fcal/issues).

To contribute

```sh
$ git clone https://github.com/5anthosh/fcal
```

```sh
$ npm install
```

### Run tests

```sh
$ npm test
```