Pattern-parser NPM

pattern-parser

What is this?

A simple npm package to match strings based on a predefined set of patterns and route parsed arguments to callbacks. No other dependencies. You can use it to implement simple message-based interactions - at least that's what I intended it to do.

How to install?

npm install pattern-parser --save

How do I use it?

var parse = require('pattern-parser')
boolean parse(string message, array patterns[, function not_found, object context])

parser takes four arguments:

a message to parse.
an array of patterns.
(optional) callback function that will be executed if no match is found. Original message is passed as an argument.
(optional) an object to be passed as a context to all callbacks. For example, if you would put { id: 123 } as a context, then every callback (including not_found) could access that parameter through this.id.

Parser will return a callback result if a match was found or false otherwise. Parser stops after the first match is found, so the order of patterns is important.

Here's how to write patterns:

var patterns = [
    {
        pattern: 'Your message pattern that can hold regular expressions and regex helpers (see below)',
        callback: function(arg1, arg2...)
        {
            // if the message is matched with this pattern, this function will be called with parsed arguments
        }
    }
];

You can use regular expressions in patterns. There are a few useful helpers to make writing patterns faster.

{string} - matches whatever.
{word} - matches exactly one word.
{number} - matches any number (integer or float).
{integer} - matches only integers.
{float} - matches only numbers with floating point.

Example

var parse = require('pattern-parser');

// an array of patterns to match to, callbacks included
var patterns = [
    {
        pattern: 'Order {integer} rolls of toilet paper',
        callback: function (rolls)
        {
            console.log('I will order ' + rolls + ' of toilet paper');
        }
    },
    {
        pattern: 'Remind me to {string} tomorrow',
        callback: function (reminder)
        {
            console.log('I will remind you to ' + reminder + ' tomorrow at noon');
        }
    }
];

// a message you want to parse
var message = 'Remind me to pay the taxes tomorrow';

// parser stops after the first match is found, so the order of patterns is important.
// matching is case-insensitive
parse(message, patterns);

// what if no match is found?
parse('Order bazillion rolls of toilet paper', patterns, function(msg) { console.log('Sorry, could not understand what you meant by: ' + msg); });