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# @rollup/plugin-replace
🍣 A Rollup plugin which replaces targeted strings in files while bundling.
## Requirements
This plugin requires an [LTS](https://github.com/nodejs/Release) Node version (v14.0.0+) and Rollup v1.20.0+.
## Install
Using npm:
```console
npm install @rollup/plugin-replace --save-dev
```
## Usage
Create a `rollup.config.js` [configuration file](https://www.rollupjs.org/guide/en/#configuration-files) and import the plugin:
```js
import replace from '@rollup/plugin-replace';
export default {
input: 'src/index.js',
output: {
dir: 'output',
format: 'cjs'
},
plugins: [
replace({
'process.env.NODE_ENV': JSON.stringify('production'),
__buildDate__: () => JSON.stringify(new Date()),
__buildVersion: 15
})
]
};
```
Then call `rollup` either via the [CLI](https://www.rollupjs.org/guide/en/#command-line-reference) or the [API](https://www.rollupjs.org/guide/en/#javascript-api).
The configuration above will replace every instance of `process.env.NODE_ENV` with `"production"` and `__buildDate__` with the result of the given function in any file included in the build.
_Note: Values must be either primitives (e.g. string, number) or `function` that returns a string. For complex values, use `JSON.stringify`. To replace a target with a value that will be evaluated as a string, set the value to a quoted string (e.g. `"test"`) or use `JSON.stringify` to preprocess the target string safely._
Typically, `@rollup/plugin-replace` should be placed in `plugins` _before_ other plugins so that they may apply optimizations, such as dead code removal.
## Options
In addition to the properties and values specified for replacement, users may also specify the options below.
### `delimiters`
Type: `Array[String, String]`<br>
Default: `['\\b', '\\b(?!\\.)']`
Specifies the boundaries around which strings will be replaced. By default, delimiters are [word boundaries](https://www.regular-expressions.info/wordboundaries.html) and also prevent replacements of instances with nested access. See [Word Boundaries](#word-boundaries) below for more information.
For example, if you pass `typeof window` in `values` to-be-replaced, then you could expect the following scenarios:
- `typeof window` **will** be replaced
- `typeof window.document` **will not** be replaced due to `(?!\.)` boundary
- `typeof windowSmth` **will not** be replaced due to a `\b` boundary
Delimiters will be used to build a `Regexp`. To match special characters (any of `.*+?^${}()|[]\`), be sure to [escape](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions#escaping) them.
### `objectGuards`
Type: `Boolean`<br>
Default: `false`
When replacing dot-separated object properties like `process.env.NODE_ENV`, will also replace `typeof process` object guard
checks against the objects with the string `"object"`.
For example:
```js
replace({
values: {
'process.env.NODE_ENV': '"production"'
}
});
```
```js
// Input
if (typeof process !== 'undefined' && process.env.NODE_ENV === 'production') {
console.log('production');
}
// Without `objectGuards`
if (typeof process !== 'undefined' && 'production' === 'production') {
console.log('production');
}
// With `objectGuards`
if ('object' !== 'undefined' && 'production' === 'production') {
console.log('production');
}
```
### `preventAssignment`
Type: `Boolean`<br>
Default: `false`
Prevents replacing strings where they are followed by a single equals sign. For example, where the plugin is called as follows:
```js
replace({
values: {
'process.env.DEBUG': 'false'
}
});
```
Observe the following code:
```js
// Input
process.env.DEBUG = false;
if (process.env.DEBUG == true) {
//
}
// Without `preventAssignment`
false = false; // this throws an error because false cannot be assigned to
if (false == true) {
//
}
// With `preventAssignment`
process.env.DEBUG = false;
if (false == true) {
//
}
```
### `exclude`
Type: `String` | `Array[...String]`<br>
Default: `null`
A [picomatch pattern](https://github.com/micromatch/picomatch), or array of patterns, which specifies the files in the build the plugin should _ignore_. By default no files are ignored.
### `include`
Type: `String` | `Array[...String]`<br>
Default: `null`
A [picomatch pattern](https://github.com/micromatch/picomatch), or array of patterns, which specifies the files in the build the plugin should operate on. By default all files are targeted.
### `values`
Type: `{ [key: String]: Replacement }`, where `Replacement` is either a string or a `function` that returns a string.
Default: `{}`
To avoid mixing replacement strings with the other options, you can specify replacements in the `values` option. For example, the following signature:
```js
replace({
include: ['src/**/*.js'],
changed: 'replaced'
});
```
Can be replaced with:
```js
replace({
include: ['src/**/*.js'],
values: {
changed: 'replaced'
}
});
```
## Word Boundaries
By default, values will only match if they are surrounded by _word boundaries_.
Consider the following options and build file:
```js
module.exports = {
...
plugins: [replace({ changed: 'replaced' })]
};
```
```js
// file.js
console.log('changed');
console.log('unchanged');
```
The result would be:
```js
// file.js
console.log('replaced');
console.log('unchanged');
```
To ignore word boundaries and replace every instance of the string, wherever it may be, specify empty strings as delimiters:
```js
export default {
...
plugins: [
replace({
changed: 'replaced',
delimiters: ['', '']
})
]
};
```
## Meta
[CONTRIBUTING](/.github/CONTRIBUTING.md)
[LICENSE (MIT)](/LICENSE)
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