pattern-expander

A JavaScript library to expand a pattern with permutations of specified values.

pattern-expander expands a pattern by applying a set of rules to it. An example: The pattern pattern-a-b and the rules

Pattern 1:
  variable: a
  values:
    - 1
    - 2
  
Pattern2:
  variable: b
  values:
    - 3
    - 4

would expand to the following results:

pattern-1-3
pattern-1-4
pattern-2-3
pattern-2-4

It's great for generating date lists, file lists, etc.

Installation

To use pattern-exoander in your project, just install it via npm:

npm install -S pattern-expander

Usage

To expand a pattern import the expand function and the Rule constructor from the pattern-expander module:

import {expand, Rule} from 'pattern-expander';

After this, set up a list of rules and expand your pattern string(s).

Create Rules

To create rules, create an Array, containing Rule objects. The Rule constructor can be used in two different ways:

• Rule(variable, values, padChar):
  • variable {String}: the variable, which should be substituted
  • values {[String]}: the values, which should be used for expansion
  • padChar {String} [Optional]: The character used for padding, if the variable block occupies more characters than the value (Default: '0')
• Rule(variable, from, to, padChar):
  • variable {String}: the variable, which should be substituted
  • from {Number}: the beginning of the numeric range used for expansion
  • to {Number}: the end of the numeric range used for expansion
  • padChar {String} [Optional]: The character used for padding, if the variable block occupies more characters than the value (Default: '0')

Example: creating two rules, which expand the variable a with the values "a" and "b", padded with xes and the variable b with the values "1" and "2"

const rules = [new Rule('a', ['a', 'b'], 'x'), new Rule('b', 1, 2)];

Expand Patterns

If you have set up your rules, just pass your pattern string (which may contain your variable(s)) or even an array of pattern strings to the expand function with the signature expand(pattern, rules). Consecutive occurrences of a variable are treated as a variable block and are just substituted once with the value and may be padded with the padChar, if the value is shorter than the variable block. If the value is longer than the variable block, it will be inserted completely.

Example:

const pattern = 'aa-b';

const result = expand(pattern, rules);
/*
result:
[
    'xa-1',
    'xa-2',
    'xb-1',
    'xb-2'
]
 */

Example

A practical example: You want to write a function, which prints out all the days of the year.

import {expand, Rule} from 'pattern-expander';

function printYear(year) {
    const pattern = 'yyyy-mm-dd';
    
    // setup the needed rules
    const yearRule = new Rule('y', [String(year)]);
    const monthRule = month => new Rule('m', [String(month)]);
    const days28DaysRule = new Rule(`d`, 1, 28); 
    const days30DaysRule = new Rule(`d`, 1, 30); 
    const days31DaysRule = new Rule(`d`, 1, 31); 
    
    // generate an Array containing the numbers 1 -12 and map the 
    // expansion rules for the months onto it and expand them
    const months = Array.from(new Array(12), (val, key) => key + 1)
        .map(month => {
            let rules = [yearRule, monthRule(month)];
            
            // add the correct rule for the month
            if (month == 1) {
                rules.push(days28DaysRule);
            } else if ((month <= 7 && month % 2 == 0) || (month > 7 && month % 2 != 0)) {
                rules.push(days30DaysRule);
            } else {
                rules.push(days31DaysRule);
            }
            
            return rules
        })
        .map(rules => expand(pattern, rules));
        
    // flatten the month array
    const days = [].concat.apply([], months);
    
    // output the days
    days.forEach(day => console.log(day));
}

calling printYear(2016) would now generate the following ouput (excerpt):

2016-01-01
2016-01-02
2016-01-03
2016-01-04
2016-01-05
2016-01-06
2016-01-07
2016-01-08
2016-01-09
2016-01-10
2016-01-11
2016-01-12
2016-01-13
2016-01-14
2016-01-15
2016-01-16
2016-01-17
2016-01-18
...
2016-12-10
2016-12-11
2016-12-12
2016-12-13
2016-12-14
2016-12-15
2016-12-16
2016-12-17
2016-12-18
2016-12-19
2016-12-20
2016-12-21
2016-12-22
2016-12-23
2016-12-24
2016-12-25
2016-12-26
2016-12-27
2016-12-28
2016-12-29
2016-12-30
2016-12-31

##License pattern-expander is offered under MIT License (Read LICENSE). Use it! :) Copyright 2016 DevWurm

##Collaborating I really appreciate any kind of collaboration! You can use the GitHub issue tracker for bugs and feature requests or create a pull request to submit changes. Forks are welcome, too! If you don't want to use these possibilities, you can also write me an email to [email protected].

Contact

If you have any questions, ideas, etc. feel free to contact me: DevWurm Email: [email protected] Jabber: [email protected] Twitter: @DevWurm