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val-loader

A webpack loader which executes a given module, and returns the result of the
execution at build-time, when the module is required in the bundle. In this way,
the loader changes a module from code to a result.

Another way to view val-loader, is that it allows a user a way to make their
own custom loader logic, without having to write a custom loader.

The target module is called with two arguments: (options, loaderContext)

- options: The loader options (for instance provided in the webpack config. See the example below).
- loaderContext: The loader context.

Getting Started

To begin, you'll need to install val-loader:

``console
npm install val-loader --save-dev
`

`console
yarn add -D val-loader
`

`console
pnpm add -D val-loader
`

Then add the loader to your webpack config. For example:

target-file.js

`js
module.exports = (options, loaderContext) => {
return { code: "module.exports = 42;" };
};
`

webpack.config.js

`js
module.exports = {
module: {
rules: [
{
test: /target-file.js$/,
use: [
{
loader: val-loader,
},
],
},
],
},
};
`

src/entry.js

`js
const answer = require("target-file");
`

And run webpack via your preferred method.

Options

- executableFile

$3

Type:

`ts
type executableFile = string;
`

Default: undefined

Allows to specify path to the executable file

data.json

`json
{
"years": "10"
}
`

executable-file.js

`js
module.exports = function yearsInMs(options, loaderContext, content) {
const { years } = JSON.parse(content);
const value = years 365 24 60 60 * 1000;

return {
cacheable: true,
code: "module.exports = " + value,
};
};
`

webpack.config.js

`js
module.exports = {
module: {
rules: [
{
test: /\.(json)$/i,
rules: [
{
loader: "val-loader",
options: {
executableFile: path.resolve(
__dirname,
"fixtures",
"executableFile.js",
),
},
},
],
},
{
test: /\.json$/i,
type: "asset/resource",
},
],
},
};
`

Return Object Properties

Targeted modules of this loader must export a Function that returns an object,
or a Promise resolving an object (e.g. async function), containing a code property at a minimum, but can
contain any number of additional properties.

$3

Type:

`ts
type code = string | Buffer;
`

Default: undefined
_Required_

Code passed along to webpack or the next loader that will replace the module.

$3

Type:

`ts
type sourceMap = object;
`

Default: undefined

A source map passed along to webpack or the next loader.

$3

Type:

`ts
type ast = Array