# fill-range [](https://www.npmjs.com/package/fill-range) [](https://npmjs.org/package/fill-range) [](https://npmjs.org/package/fill-range) [](https://travis-ci.org/jonschlinkert/fill-range)
> Fill in a range of numbers or letters, optionally passing an increment or multiplier to use.
Please consider following this project's author, [Jon Schlinkert](https://github.com/jonschlinkert), and consider starring the project to show your :heart: and support.
- [Install](#install)
- [Usage](#usage)
* [Invalid ranges](#invalid-ranges)
* [Custom function](#custom-function)
* [Special characters](#special-characters)
+ [plus](#plus)
+ [pipe and tilde](#pipe-and-tilde)
+ [angle bracket](#angle-bracket)
+ [question mark](#question-mark)
- [About](#about)
_(TOC generated by [verb](https://github.com/verbose/verb) using [markdown-toc](https://github.com/jonschlinkert/markdown-toc))_
## Install
Install with [npm](https://www.npmjs.com/):
```sh
$ npm install --save fill-range
```
## Usage
```js
var range = require('fill-range');
range('a', 'e');
//=> ['a', 'b', 'c', 'd', 'e']
```
**Params**
```js
range(start, stop, step, options, fn);
```
* `start`: **{String|Number}** the number or letter to start with
* `end`: **{String|Number}** the number or letter to end with
* `step`: **{String|Number}** optionally pass the step to use. works for letters or numbers.
* `options`: **{Object}**:
- `makeRe`: return a regex-compatible string (still returned as an array for consistency)
- `step`: pass the step on the options as an alternative to passing it as an argument
- `silent`: `true` by default, set to false to throw errors for invalid ranges.
* `fn`: **{Function}** optionally [pass a function](#custom-function) to modify each character
**Examples**
```js
range(1, 3)
//=> ['1', '2', '3']
range('1', '3')
//=> ['1', '2', '3']
range('0', '-5')
//=> [ '0', '-1', '-2', '-3', '-4', '-5' ]
range(-9, 9, 3)
//=> [ '-9', '-6', '-3', '0', '3', '6', '9' ])
range('-1', '-10', '-2')
//=> [ '-1', '-3', '-5', '-7', '-9' ]
range('1', '10', '2')
//=> [ '1', '3', '5', '7', '9' ]
range('a', 'e')
//=> ['a', 'b', 'c', 'd', 'e']
range('a', 'e', 2)
//=> ['a', 'c', 'e']
range('A', 'E', 2)
//=> ['A', 'C', 'E']
```
### Invalid ranges
When an invalid range is passed, `null` is returned.
```js
range('1.1', '2');
//=> null
range('a', '2');
//=> null
range(1, 10, 'foo');
//=> null
```
If you want errors to be throw, pass `silent: false` on the options:
### Custom function
Optionally pass a custom function as the third or fourth argument:
```js
range('a', 'e', function (val, isNumber, pad, i) {
if (!isNumber) {
return String.fromCharCode(val) + i;
}
return val;
});
//=> ['a0', 'b1', 'c2', 'd3', 'e4']
```
### Special characters
A special character may be passed as the third arg instead of a step increment. These characters can be pretty useful for brace expansion, creating file paths, test fixtures and similar use case.
```js
range('a', 'z', SPECIAL_CHARACTER_HERE);
```
**Supported characters**
* `+`: repeat the given string `n` times
* `|`: create a regex-ready string, instead of an array
* `>`: join values to single array element
* `?`: randomize the given pattern using [randomatic]
#### plus
Character: _(`+`)_
Repeat the first argument the number of times passed on the second argument.
**Examples:**
```js
range('a', 3, '+');
//=> ['a', 'a', 'a']
range('abc', 2, '+');
//=> ['abc', 'abc']
```
#### pipe and tilde
Characters: _(`|` and `~`)_
Creates a regex-capable string (either a logical `or` or a character class) from the expanded arguments.
**Examples:**
```js
range('a', 'c', '|');
//=> ['(a|b|c)'
range('a', 'c', '~');
//=> ['[a-c]'
range('a', 'z', '|5');
//=> ['(a|f|k|p|u|z)'
```
**Automatic separator correction**
To avoid this error:
> `Range out of order in character class`
Fill-range detects invalid sequences and uses the correct syntax. For example:
**invalid** (regex)
If you pass these:
```js
range('a', 'z', '~5');
// which would result in this
//=> ['[a-f-k-p-u-z]']
range('10', '20', '~');
// which would result in this
//=> ['[10-20]']
```
**valid** (regex)
fill-range corrects them to this:
```js
range('a', 'z', '~5');
//=> ['(a|f|k|p|u|z)'
range('10', '20', '~');
//=> ['(10-20)'
```
#### angle bracket
Character: _(`>`)_
Joins all values in the returned array to a single value.
**Examples:**
```js
range('a', 'e', '>');
//=> ['abcde']
range('5', '8', '>');
//=> ['5678']
range('2', '20', '2>');
//=> ['2468101214161820']
```
#### question mark
Character: _(`?`)_
Uses [randomatic] to generate randomized alpha, numeric, or alpha-numeric patterns based on the provided arguments.
**Examples:**
_(actual results would obviously be randomized)_
Generate a 5-character, uppercase, alphabetical string:
```js
range('A', 5, '?');
//=> ['NSHAK']
```
Generate a 5-digit random number:
```js
range('0', 5, '?');
//=> ['36583']
```
Generate a 10-character alpha-numeric string:
```js
range('A0', 10, '?');
//=> ['5YJD60VQNN']
```
See the [randomatic] repo for all available options and or to create issues or feature requests related to randomization.
## About
Contributing
Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](../../issues/new).
Running Tests
Running and reviewing unit tests is a great way to get familiarized with a library and its API. You can install dependencies and run tests with the following command:
```sh
$ npm install && npm test
```
Building docs
_(This project's readme.md is generated by [verb](https://github.com/verbose/verb-generate-readme), please don't edit the readme directly. Any changes to the readme must be made in the [.verb.md](.verb.md) readme template.)_
To generate the readme, run the following command:
```sh
$ npm install -g verbose/verb#dev verb-generate-readme && verb
```
### Related projects
You might also be interested in these projects:
* [braces](https://www.npmjs.com/package/braces): Bash-like brace expansion, implemented in JavaScript. Safer than other brace expansion libs, with complete support… [more](https://github.com/micromatch/braces) | [homepage](https://github.com/micromatch/braces "Bash-like brace expansion, implemented in JavaScript. Safer than other brace expansion libs, with complete support for the Bash 4.3 braces specification, without sacrificing speed.")
* [expand-range](https://www.npmjs.com/package/expand-range): Fast, bash-like range expansion. Expand a range of numbers or letters, uppercase or lowercase. Used… [more](https://github.com/jonschlinkert/expand-range) | [homepage](https://github.com/jonschlinkert/expand-range "Fast, bash-like range expansion. Expand a range of numbers or letters, uppercase or lowercase. Used by [micromatch].")
* [is-glob](https://www.npmjs.com/package/is-glob): Returns `true` if the given string looks like a glob pattern or an extglob pattern… [more](https://github.com/jonschlinkert/is-glob) | [homepage](https://github.com/jonschlinkert/is-glob "Returns `true` if the given string looks like a glob pattern or an extglob pattern. This makes it easy to create code that only uses external modules like node-glob when necessary, resulting in much faster code execution and initialization time, and a bet")
* [micromatch](https://www.npmjs.com/package/micromatch): Glob matching for javascript/node.js. A drop-in replacement and faster alternative to minimatch and multimatch. | [homepage](https://github.com/micromatch/micromatch "Glob matching for javascript/node.js. A drop-in replacement and faster alternative to minimatch and multimatch.")
### Contributors
| **Commits** | **Contributor** |
| --- | --- |
| 111 | [jonschlinkert](https://github.com/jonschlinkert) |
| 2 | [paulmillr](https://github.com/paulmillr) |
| 1 | [edorivai](https://github.com/edorivai) |
| 1 | [realityking](https://github.com/realityking) |
| 1 | [wtgtybhertgeghgtwtg](https://github.com/wtgtybhertgeghgtwtg) |
### Author
**Jon Schlinkert**
* [LinkedIn Profile](https://linkedin.com/in/jonschlinkert)
* [GitHub Profile](https://github.com/jonschlinkert)
* [Twitter Profile](https://twitter.com/jonschlinkert)
### License
Copyright © 2018, [Jon Schlinkert](https://github.com/jonschlinkert).
Released under the [MIT License](LICENSE).
***
_This file was generated by [verb-generate-readme](https://github.com/verbose/verb-generate-readme), v0.6.0, on May 08, 2018._