1 | # detect-indent [![Build Status](https://travis-ci.org/sindresorhus/detect-indent.svg?branch=master)](https://travis-ci.org/sindresorhus/detect-indent)
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2 |
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3 | > Detect the indentation of code
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4 |
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5 | Pass in a string of any kind of text and get the indentation.
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6 |
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7 |
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8 | ## Use cases
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9 |
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10 | - Persisting the indentation when modifying a file.
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11 | - Have new content match the existing indentation.
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12 | - Setting the right indentation in your editor.
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13 |
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14 |
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15 | ## Install
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16 |
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17 | ```
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18 | $ npm install --save detect-indent
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19 | ```
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20 |
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21 |
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22 | ## Usage
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23 |
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24 | Here we modify a JSON file while persisting the indentation:
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25 |
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26 | ```js
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27 | const fs = require('fs');
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28 | const detectIndent = require('detect-indent');
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29 |
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30 | /*
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31 | {
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32 | "ilove": "pizza"
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33 | }
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34 | */
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35 | const file = fs.readFileSync('foo.json', 'utf8');
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36 |
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37 | // tries to detect the indentation and falls back to a default if it can't
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38 | const indent = detectIndent(file).indent || ' ';
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39 |
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40 | const json = JSON.parse(file);
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41 |
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42 | json.ilove = 'unicorns';
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43 |
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44 | fs.writeFileSync('foo.json', JSON.stringify(json, null, indent));
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45 | /*
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46 | {
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47 | "ilove": "unicorns"
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48 | }
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49 | */
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50 | ```
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51 |
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52 |
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53 | ## API
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54 |
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55 | Accepts a string and returns an object with stats about the indentation:
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56 |
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57 | * `amount` {number} - Amount of indentation, for example `2`
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58 | * `type` {string|null} - Type of indentation. Possible values are `tab`, `space` or `null` if no indentation is detected
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59 | * `indent` {string} - Actual indentation
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60 |
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61 |
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62 | ## Algorithm
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63 |
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64 | The current algorithm looks for the most common difference between two consecutive non-empty lines.
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65 |
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66 | In the following example, even if the 4-space indentation is used 3 times whereas the 2-space one is used 2 times, it is detected as less used because there were only 2 differences with this value instead of 4 for the 2-space indentation:
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67 |
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68 | ```css
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69 | html {
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70 | box-sizing: border-box;
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71 | }
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72 |
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73 | body {
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74 | background: gray;
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75 | }
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76 |
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77 | p {
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78 | line-height: 1.3em;
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79 | margin-top: 1em;
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80 | text-indent: 2em;
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81 | }
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82 | ```
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83 |
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84 | [Source.](https://medium.com/@heatherarthur/detecting-code-indentation-eff3ed0fb56b#3918)
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85 |
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86 | Furthermore, if there are more than one most used difference, the indentation with the most lines is selected.
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87 |
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88 | In the following example, the indentation is detected as 4-spaces:
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89 |
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90 | ```css
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91 | body {
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92 | background: gray;
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93 | }
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94 |
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95 | p {
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96 | line-height: 1.3em;
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97 | margin-top: 1em;
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98 | text-indent: 2em;
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99 | }
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100 | ```
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101 |
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102 |
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103 | ## Related
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104 |
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105 | - [detect-indent-cli](https://github.com/sindresorhus/detect-indent-cli) - CLI for this module
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106 | - [detect-newline](https://github.com/sindresorhus/detect-newline) - Detect the dominant newline character of a string
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107 |
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108 |
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109 | ## License
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110 |
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111 | MIT © [Sindre Sorhus](https://sindresorhus.com)
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