| # fill-range [](https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=W8YFZ425KND68) [](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) |
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| > Fill in a range of numbers or letters, optionally passing an increment or `step` to use, or create a regex-compatible range with `options.toRegex` |
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| Please consider following this project's author, [Jon Schlinkert](https://github.com/jonschlinkert), and consider starring the project to show your :heart: and support. |
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| ## Install |
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| Install with [npm](https://www.npmjs.com/): |
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| ```sh |
| $ npm install --save fill-range |
| ``` |
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| ## Usage |
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| Expands numbers and letters, optionally using a `step` as the last argument. _(Numbers may be defined as JavaScript numbers or strings)_. |
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| ```js |
| const fill = require('fill-range'); |
| // fill(from, to[, step, options]); |
| |
| console.log(fill('1', '10')); //=> ['1', '2', '3', '4', '5', '6', '7', '8', '9', '10'] |
| console.log(fill('1', '10', { toRegex: true })); //=> [1-9]|10 |
| ``` |
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| **Params** |
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| * `from`: **{String|Number}** the number or letter to start with |
| * `to`: **{String|Number}** the number or letter to end with |
| * `step`: **{String|Number|Object|Function}** Optionally pass a [step](#optionsstep) to use. |
| * `options`: **{Object|Function}**: See all available [options](#options) |
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| ## Examples |
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| By default, an array of values is returned. |
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| **Alphabetical ranges** |
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| ```js |
| console.log(fill('a', 'e')); //=> ['a', 'b', 'c', 'd', 'e'] |
| console.log(fill('A', 'E')); //=> [ 'A', 'B', 'C', 'D', 'E' ] |
| ``` |
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| **Numerical ranges** |
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| Numbers can be defined as actual numbers or strings. |
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| ```js |
| console.log(fill(1, 5)); //=> [ 1, 2, 3, 4, 5 ] |
| console.log(fill('1', '5')); //=> [ 1, 2, 3, 4, 5 ] |
| ``` |
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| **Negative ranges** |
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| Numbers can be defined as actual numbers or strings. |
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| ```js |
| console.log(fill('-5', '-1')); //=> [ '-5', '-4', '-3', '-2', '-1' ] |
| console.log(fill('-5', '5')); //=> [ '-5', '-4', '-3', '-2', '-1', '0', '1', '2', '3', '4', '5' ] |
| ``` |
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| **Steps (increments)** |
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| ```js |
| // numerical ranges with increments |
| console.log(fill('0', '25', 4)); //=> [ '0', '4', '8', '12', '16', '20', '24' ] |
| console.log(fill('0', '25', 5)); //=> [ '0', '5', '10', '15', '20', '25' ] |
| console.log(fill('0', '25', 6)); //=> [ '0', '6', '12', '18', '24' ] |
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| // alphabetical ranges with increments |
| console.log(fill('a', 'z', 4)); //=> [ 'a', 'e', 'i', 'm', 'q', 'u', 'y' ] |
| console.log(fill('a', 'z', 5)); //=> [ 'a', 'f', 'k', 'p', 'u', 'z' ] |
| console.log(fill('a', 'z', 6)); //=> [ 'a', 'g', 'm', 's', 'y' ] |
| ``` |
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| ## Options |
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| ### options.step |
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| **Type**: `number` (formatted as a string or number) |
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| **Default**: `undefined` |
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| **Description**: The increment to use for the range. Can be used with letters or numbers. |
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| **Example(s)** |
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| ```js |
| // numbers |
| console.log(fill('1', '10', 2)); //=> [ '1', '3', '5', '7', '9' ] |
| console.log(fill('1', '10', 3)); //=> [ '1', '4', '7', '10' ] |
| console.log(fill('1', '10', 4)); //=> [ '1', '5', '9' ] |
| |
| // letters |
| console.log(fill('a', 'z', 5)); //=> [ 'a', 'f', 'k', 'p', 'u', 'z' ] |
| console.log(fill('a', 'z', 7)); //=> [ 'a', 'h', 'o', 'v' ] |
| console.log(fill('a', 'z', 9)); //=> [ 'a', 'j', 's' ] |
| ``` |
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| ### options.strictRanges |
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| **Type**: `boolean` |
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| **Default**: `false` |
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| **Description**: By default, `null` is returned when an invalid range is passed. Enable this option to throw a `RangeError` on invalid ranges. |
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| **Example(s)** |
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| The following are all invalid: |
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| ```js |
| fill('1.1', '2'); // decimals not supported in ranges |
| fill('a', '2'); // incompatible range values |
| fill(1, 10, 'foo'); // invalid "step" argument |
| ``` |
| |
| ### options.stringify |
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| **Type**: `boolean` |
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| **Default**: `undefined` |
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| **Description**: Cast all returned values to strings. By default, integers are returned as numbers. |
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| **Example(s)** |
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| ```js |
| console.log(fill(1, 5)); //=> [ 1, 2, 3, 4, 5 ] |
| console.log(fill(1, 5, { stringify: true })); //=> [ '1', '2', '3', '4', '5' ] |
| ``` |
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| ### options.toRegex |
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| **Type**: `boolean` |
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| **Default**: `undefined` |
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| **Description**: Create a regex-compatible source string, instead of expanding values to an array. |
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| **Example(s)** |
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| ```js |
| // alphabetical range |
| console.log(fill('a', 'e', { toRegex: true })); //=> '[a-e]' |
| // alphabetical with step |
| console.log(fill('a', 'z', 3, { toRegex: true })); //=> 'a|d|g|j|m|p|s|v|y' |
| // numerical range |
| console.log(fill('1', '100', { toRegex: true })); //=> '[1-9]|[1-9][0-9]|100' |
| // numerical range with zero padding |
| console.log(fill('000001', '100000', { toRegex: true })); |
| //=> '0{5}[1-9]|0{4}[1-9][0-9]|0{3}[1-9][0-9]{2}|0{2}[1-9][0-9]{3}|0[1-9][0-9]{4}|100000' |
| ``` |
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| ### options.transform |
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| **Type**: `function` |
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| **Default**: `undefined` |
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| **Description**: Customize each value in the returned array (or [string](#optionstoRegex)). _(you can also pass this function as the last argument to `fill()`)_. |
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| **Example(s)** |
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| ```js |
| // add zero padding |
| console.log(fill(1, 5, value => String(value).padStart(4, '0'))); |
| //=> ['0001', '0002', '0003', '0004', '0005'] |
| ``` |
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| ## About |
| |
| <details> |
| <summary><strong>Contributing</strong></summary> |
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| Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](../../issues/new). |
| |
| </details> |
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| <details> |
| <summary><strong>Running Tests</strong></summary> |
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| 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: |
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| ```sh |
| $ npm install && npm test |
| ``` |
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| </details> |
| |
| <details> |
| <summary><strong>Building docs</strong></summary> |
| |
| _(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.)_ |
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| To generate the readme, run the following command: |
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| ```sh |
| $ npm install -g verbose/verb#dev verb-generate-readme && verb |
| ``` |
| |
| </details> |
| |
| ### Contributors |
| |
| | **Commits** | **Contributor** | |
| | --- | --- | |
| | 116 | [jonschlinkert](https://github.com/jonschlinkert) | |
| | 4 | [paulmillr](https://github.com/paulmillr) | |
| | 2 | [realityking](https://github.com/realityking) | |
| | 2 | [bluelovers](https://github.com/bluelovers) | |
| | 1 | [edorivai](https://github.com/edorivai) | |
| | 1 | [wtgtybhertgeghgtwtg](https://github.com/wtgtybhertgeghgtwtg) | |
| |
| ### Author |
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| **Jon Schlinkert** |
| |
| * [GitHub Profile](https://github.com/jonschlinkert) |
| * [Twitter Profile](https://twitter.com/jonschlinkert) |
| * [LinkedIn Profile](https://linkedin.com/in/jonschlinkert) |
| |
| Please consider supporting me on Patreon, or [start your own Patreon page](https://patreon.com/invite/bxpbvm)! |
| |
| <a href="https://www.patreon.com/jonschlinkert"> |
| <img src="https://c5.patreon.com/external/logo/become_a_patron_button@2x.png" height="50"> |
| </a> |
| |
| ### License |
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| Copyright © 2019, [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), v0.8.0, on April 08, 2019._ |