1 | # magic-string
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2 |
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3 | <p align="center">
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4 | <a href="https://travis-ci.org/Rich-Harris/magic-string">
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5 | <img src="http://img.shields.io/travis/Rich-Harris/magic-string.svg"
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6 | alt="build status">
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7 | </a>
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8 | <a href="https://npmjs.org/package/magic-string">
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9 | <img src="https://img.shields.io/npm/v/magic-string.svg"
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10 | alt="npm version">
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11 | </a>
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12 | <a href="https://github.com/Rich-Harris/magic-string/blob/master/LICENSE.md">
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13 | <img src="https://img.shields.io/npm/l/magic-string.svg"
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14 | alt="license">
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15 | </a>
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16 | <a href="https://david-dm.org/Rich-Harris/magic-string">
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17 | <img src="https://david-dm.org/Rich-Harris/magic-string.svg"
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18 | alt="dependency status">
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19 | </a>
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20 | <a href="http://codecov.io/github/Rich-Harris/magic-string?branch=master">
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21 | <img src="http://codecov.io/github/Rich-Harris/magic-string/coverage.svg?branch=master" alt="Coverage via Codecov" />
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22 | </a>
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23 | </p>
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24 |
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25 | Suppose you have some source code. You want to make some light modifications to it - replacing a few characters here and there, wrapping it with a header and footer, etc - and ideally you'd like to generate a source map at the end of it. You've thought about using something like [recast](https://github.com/benjamn/recast) (which allows you to generate an AST from some JavaScript, manipulate it, and reprint it with a sourcemap without losing your comments and formatting), but it seems like overkill for your needs (or maybe the source code isn't JavaScript).
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26 |
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27 | Your requirements are, frankly, rather niche. But they're requirements that I also have, and for which I made magic-string. It's a small, fast utility for manipulating strings and generating sourcemaps.
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28 |
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29 | ## Installation
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30 |
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31 | magic-string works in both node.js and browser environments. For node, install with npm:
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32 |
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33 | ```bash
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34 | npm i magic-string
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35 | ```
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36 |
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37 | To use in browser, grab the [magic-string.umd.js](https://unpkg.com/magic-string/dist/magic-string.umd.js) file and add it to your page:
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38 |
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39 | ```html
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40 | <script src='magic-string.umd.js'></script>
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41 | ```
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42 |
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43 | (It also works with various module systems, if you prefer that sort of thing - it has a dependency on [vlq](https://github.com/Rich-Harris/vlq).)
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44 |
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45 | ## Usage
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46 |
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47 | These examples assume you're in node.js, or something similar:
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48 |
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49 | ```js
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50 | var MagicString = require( 'magic-string' );
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51 | var s = new MagicString( 'problems = 99' );
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52 |
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53 | s.overwrite( 0, 8, 'answer' );
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54 | s.toString(); // 'answer = 99'
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55 |
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56 | s.overwrite( 11, 13, '42' ); // character indices always refer to the original string
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57 | s.toString(); // 'answer = 42'
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58 |
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59 | s.prepend( 'var ' ).append( ';' ); // most methods are chainable
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60 | s.toString(); // 'var answer = 42;'
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61 |
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62 | var map = s.generateMap({
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63 | source: 'source.js',
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64 | file: 'converted.js.map',
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65 | includeContent: true
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66 | }); // generates a v3 sourcemap
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67 |
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68 | require( 'fs' ).writeFile( 'converted.js', s.toString() );
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69 | require( 'fs' ).writeFile( 'converted.js.map', map.toString() );
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70 | ```
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71 |
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72 | You can pass an options argument:
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73 |
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74 | ```js
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75 | var s = new MagicString( someCode, {
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76 | // both these options will be used if you later
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77 | // call `bundle.addSource( s )` - see below
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78 | filename: 'foo.js',
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79 | indentExclusionRanges: [/*...*/]
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80 | });
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81 | ```
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82 |
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83 | ## Methods
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84 |
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85 | ### s.addSourcemapLocation( index )
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86 |
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87 | Adds the specified character index (with respect to the original string) to sourcemap mappings, if `hires` is `false` (see below).
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88 |
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89 | ### s.append( content )
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90 |
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91 | Appends the specified content to the end of the string. Returns `this`.
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92 |
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93 | ### s.appendLeft( index, content )
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94 |
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95 | Appends the specified `content` at the `index` in the original string. If a range *ending* with `index` is subsequently moved, the insert will be moved with it. Returns `this`. See also `s.prependLeft(...)`.
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96 |
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97 | ### s.appendRight( index, content )
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98 |
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99 | Appends the specified `content` at the `index` in the original string. If a range *starting* with `index` is subsequently moved, the insert will be moved with it. Returns `this`. See also `s.prependRight(...)`.
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100 |
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101 | ### s.clone()
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102 |
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103 | Does what you'd expect.
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104 |
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105 | ### s.generateMap( options )
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106 |
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107 | Generates a [version 3 sourcemap](https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit). All options are, well, optional:
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108 |
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109 | * `file` - the filename where you plan to write the sourcemap
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110 | * `source` - the filename of the file containing the original source
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111 | * `includeContent` - whether to include the original content in the map's `sourcesContent` array
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112 | * `hires` - whether the mapping should be high-resolution. Hi-res mappings map every single character, meaning (for example) your devtools will always be able to pinpoint the exact location of function calls and so on. With lo-res mappings, devtools may only be able to identify the correct line - but they're quicker to generate and less bulky. If sourcemap locations have been specified with `s.addSourceMapLocation()`, they will be used here.
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113 |
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114 | The returned sourcemap has two (non-enumerable) methods attached for convenience:
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115 |
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116 | * `toString` - returns the equivalent of `JSON.stringify(map)`
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117 | * `toUrl` - returns a DataURI containing the sourcemap. Useful for doing this sort of thing:
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118 |
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119 | ```js
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120 | code += '\n//# sourceMappingURL=' + map.toUrl();
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121 | ```
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122 |
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123 | ### s.indent( prefix[, options] )
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124 |
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125 | Prefixes each line of the string with `prefix`. If `prefix` is not supplied, the indentation will be guessed from the original content, falling back to a single tab character. Returns `this`.
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126 |
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127 | The `options` argument can have an `exclude` property, which is an array of `[start, end]` character ranges. These ranges will be excluded from the indentation - useful for (e.g.) multiline strings.
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128 |
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129 | ### s.insertLeft( index, content )
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130 |
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131 | **DEPRECATED** since 0.17 – use `s.appendLeft(...)` instead
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132 |
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133 | ### s.insertRight( index, content )
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134 |
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135 | **DEPRECATED** since 0.17 – use `s.prependRight(...)` instead
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136 |
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137 | ### s.locate( index )
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138 |
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139 | **DEPRECATED** since 0.10 – see [#30](https://github.com/Rich-Harris/magic-string/pull/30)
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140 |
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141 | ### s.locateOrigin( index )
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142 |
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143 | **DEPRECATED** since 0.10 – see [#30](https://github.com/Rich-Harris/magic-string/pull/30)
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144 |
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145 | ### s.move( start, end, newIndex )
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146 |
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147 | Moves the characters from `start` and `end` to `index`. Returns `this`.
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148 |
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149 | ### s.overwrite( start, end, content[, options] )
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150 |
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151 | Replaces the characters from `start` to `end` with `content`. The same restrictions as `s.remove()` apply. Returns `this`.
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152 |
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153 | The fourth argument is optional. It can have a `storeName` property — if `true`, the original name will be stored for later inclusion in a sourcemap's `names` array — and a `contentOnly` property which determines whether only the content is overwritten, or anything that was appended/prepended to the range as well.
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154 |
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155 | ### s.prepend( content )
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156 |
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157 | Prepends the string with the specified content. Returns `this`.
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158 |
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159 | ### s.prependLeft ( index, content )
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160 |
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161 | Same as `s.appendLeft(...)`, except that the inserted content will go *before* any previous appends or prepends at `index`
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162 |
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163 | ### s.prependRight ( index, content )
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164 |
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165 | Same as `s.appendRight(...)`, except that the inserted content will go *before* any previous appends or prepends at `index`
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166 |
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167 | ### s.remove( start, end )
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168 |
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169 | Removes the characters from `start` to `end` (of the original string, **not** the generated string). Removing the same content twice, or making removals that partially overlap, will cause an error. Returns `this`.
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170 |
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171 | ### s.slice( start, end )
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172 |
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173 | Returns the content of the generated string that corresponds to the slice between `start` and `end` of the original string. Throws error if the indices are for characters that were already removed.
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174 |
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175 | ### s.snip( start, end )
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176 |
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177 | Returns a clone of `s`, with all content before the `start` and `end` characters of the original string removed.
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178 |
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179 | ### s.toString()
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180 |
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181 | Returns the generated string.
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182 |
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183 | ### s.trim([ charType ])
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184 |
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185 | Trims content matching `charType` (defaults to `\s`, i.e. whitespace) from the start and end. Returns `this`.
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186 |
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187 | ### s.trimStart([ charType ])
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188 |
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189 | Trims content matching `charType` (defaults to `\s`, i.e. whitespace) from the start. Returns `this`.
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190 |
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191 | ### s.trimEnd([ charType ])
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192 |
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193 | Trims content matching `charType` (defaults to `\s`, i.e. whitespace) from the end. Returns `this`.
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194 |
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195 | ### s.trimLines()
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196 |
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197 | Removes empty lines from the start and end. Returns `this`.
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198 |
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199 | ## Bundling
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200 |
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201 | To concatenate several sources, use `MagicString.Bundle`:
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202 |
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203 | ```js
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204 | var bundle = new MagicString.Bundle();
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205 |
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206 | bundle.addSource({
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207 | filename: 'foo.js',
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208 | content: new MagicString( 'var answer = 42;' )
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209 | });
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210 |
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211 | bundle.addSource({
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212 | filename: 'bar.js',
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213 | content: new MagicString( 'console.log( answer )' )
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214 | });
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215 |
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216 | // Advanced: a source can include an `indentExclusionRanges` property
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217 | // alongside `filename` and `content`. This will be passed to `s.indent()`
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218 | // - see documentation above
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219 |
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220 | bundle.indent() // optionally, pass an indent string, otherwise it will be guessed
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221 | .prepend( '(function () {\n' )
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222 | .append( '}());' );
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223 |
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224 | bundle.toString();
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225 | // (function () {
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226 | // var answer = 42;
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227 | // console.log( answer );
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228 | // }());
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229 |
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230 | // options are as per `s.generateMap()` above
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231 | var map = bundle.generateMap({
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232 | file: 'bundle.js',
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233 | includeContent: true,
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234 | hires: true
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235 | });
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236 | ```
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237 |
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238 | As an alternative syntax, if you a) don't have `filename` or `indentExclusionRanges` options, or b) passed those in when you used `new MagicString(...)`, you can simply pass the `MagicString` instance itself:
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239 |
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240 | ```js
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241 | var bundle = new MagicString.Bundle();
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242 | var source = new MagicString( someCode, {
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243 | filename: 'foo.js'
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244 | });
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245 |
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246 | bundle.addSource( source );
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247 | ```
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248 |
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249 | ## License
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250 |
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251 | MIT
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