80 lines
2.7 KiB
Markdown
80 lines
2.7 KiB
Markdown
# require-in-the-middle
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Hook into the Node.js `require` function. This allows you to modify
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modules on-the-fly as they are being required.
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[](https://www.npmjs.com/package/require-in-the-middle)
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[](https://github.com/elastic/require-in-the-middle/actions)
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## Installation
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```
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npm install require-in-the-middle --save
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```
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## Usage
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```js
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const path = require('path')
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const Hook = require('require-in-the-middle')
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// Hook into the express and mongodb module
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Hook(['express', 'mongodb'], function (exports, name, basedir) {
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const version = require(path.join(basedir, 'package.json')).version
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console.log('loading %s@%s', name, version)
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// expose the module version as a property on its exports object
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exports._version = version
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// whatever you return will be returned by `require`
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return exports
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})
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```
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## API
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The require-in-the-middle module exposes a single function:
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### `hook = Hook([modules][, options], onrequire)`
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When called a `hook` object is returned.
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Arguments:
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- `modules` <string[]> An optional array of module names to limit which modules
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trigger a call of the `onrequire` callback. If specified, this must be the
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first argument. Both regular modules (e.g. `react-dom`) and
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sub-modules (e.g. `react-dom/server`) can be specified in the array.
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- `options` <Object> An optional object containing fields that change when the
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`onrequire` callback is called. If specified, this must be the second
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argument.
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- `options.internals` <boolean> Specifies whether `onrequire` should be called
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when module-internal files are loaded; defaults to `false`.
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- `onrequire` <Function> The function to call when a module is required.
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The `onrequire` callback will be called the first time a module is
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required. The function is called with three arguments:
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- `exports` <Object> The value of the `module.exports` property that would
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normally be exposed by the required module.
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- `name` <string> The name of the module being required. If `options.internals`
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was set to `true`, the path of module-internal files that are loaded
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(relative to `basedir`) will be appended to the module name, separated by
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`path.sep`.
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- `basedir` <string> The directory where the module is located, or `undefined`
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for core modules.
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Return the value you want the module to expose (normally the `exports`
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argument).
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### `hook.unhook()`
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Removes the `onrequire` callback so that it will not be triggerd by
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subsequent calls to `require()`.
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## License
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[MIT](https://github.com/elastic/require-in-the-middle/blob/master/LICENSE)
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