Expression.js

Expression.js is an expression parser which permit to make and evaluate mathematical expressions using variables and functions.

How to use

First, download the main expression.js file. Then, include it in your HTML page :

<script type="text/javascript" src="expression.js"></script>

Or in your Node.js script :

var Expression = require('./expression.js');

Features

Simple Operations

Here is a code sample :

var parsed = Expression.parse('2 + 8 / 5'); // Parse the expression
// Do some stuff here...
var result = Expression.eval(result);       // And evaluate it

// ==== OR ====
var result = Expression.exec('2 + 8 / 5');

The point of parsing an expression before evaluating it is performances. If you have to evaluate multiple expressions at a time, you can parse it at the beginning of your task, and then evaluate it. NOTE : The longest part is the parsing.

Variables

You can also use variables, like :

Expression.exec('2 + 8 / (6 + 2)', {a: 5}); // Output: 3

If you want to prepare the expression before running it, do :

var parsed = Expression.parse('2 + 8 / (6 + 2)');
// Do some stuff...
Expression.eval(parsed, {a: 5}); // Output: 3

Strings

Expressions can contain only numbers or only strings. If you want to use strings, your code should be :

Expression.exec('"Hello" + "World"');

You MUST use the " symbol to define strings. The ' symbol will not work. NOTE : Only the '+' operator works in this context. The '-' '*' '/' operators does not work.

Functions

Now, let's see how the functions works. If you want, for example, to use the cube function, do :

Expression.exec('3 * cube(5) / 10', { cube: function(n) { return n * n * n; } }); // Output: 37.5

You can also use cosine functions, round...

ClementNerma / Expression.js