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https://github.com/line/grow-loader

A webpack loader to split class methods by decorators
https://github.com/line/grow-loader

javascript loader webpack

Last synced: about 2 months ago
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A webpack loader to split class methods by decorators

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# grow-loader

[![Travis CI](https://travis-ci.org/line/grow-loader.svg?branch=master)](https://travis-ci.org/line/grow-loader) [![npm version](https://badge.fury.io/js/grow-loader.svg)](https://badge.fury.io/js/grow-loader)

The `grow-loader` is a webpack loader to let you split "growable" methods into separate files, by simply adding a decorator to the methods in class declarations.

By "growable methods", we mean the methods that need to be dynamically imported. To learn more about dynamic import, read [this document](https://webpack.js.org/guides/code-splitting/#dynamic-imports) from webpack.

Learn more about grow-loader:

- [Installing grow-loader](#installing-grow-loader)
- [Using grow-loader](#using-grow-loader)
- [Background story](#background-story)
- [Contributing](#Contributing)
- [License](#License)

## Installing grow-loader
To install grow-loader, run the following command on your terminal.

```
npm install --save-dev "grow-loader"
```

## Using grow-loader

- [Getting started](#getting-started)
- [Customizing loader options](#customizing-loader-options)

### Getting started
1. In your webpack config, add `grow-loader` _before_ the `babel-loader`.

> Note. Webpack chains loaders from right to left, so to run a loader before another loader, it should be put latter. See https://webpack.js.org/configuration/module/#rule-use for more information.

**webpack.config.js**
```js
{
test: /\.jsx?$/,
use: [
'babel-loader',
'grow-loader'
]
}
```

2. Add the `@grow` decorator to your class methods that need to "grow". The functions marked will be split into separate files.

```js
class SampleClass {

@grow
methodToGrow() {
// ...
}

@grow
methodToGrowAndBind = () => {
// ...
}

methodToBeBundled(){

}
}
```

If you use any linter tool before grow-loader, you may use the following import statement (which does nothing) to avoid syntax error.

```js
import grow from 'grow-loader/lib/grow';
```

3. To install split functions back, call the `grow()` function.

```js
const sample = new SampleClass();
console.assert(a.methodToGrow === undefined);
console.assert(a.methodToGrowAndBind === undefined);

sample.grow().then(() => {
sample.methodToGrow();
sample.methodToGrowAndBind();
});
```

### Customizing loader options

To avoid naming conflicts, you can customize the following grow-loader options.

| Option | Default Value | Description |
| -------|---------|-------------|
| methodName | `grow` | The name of the method to be called before a split method. e.g. `grow()` |
| decoratorName | `grow` | The decorator to be detected. e.g. `@grow`. |

The grow-loader options are to be defined in your webpack config or in an `import` statement.

> Note. Learn more about configuring loaders from the [webpack documentation on loaders](https://webpack.js.org/concepts/loaders/).

The following is an example of customizing the grow method as `myGrow()` and the decorator as `@myGrowDec`.

```js
{
test: /\.jsx?$/,
use: [
'babel-loader',
'grow-loader?methodName=myGrow&decoratorName=myGrowDec'
]
}
```

## React Component Example
Using grow-loader to code-split requires only a few modifications to your code. Here is an example:

**Before applying grow-loader**

```js
export default class A extends React.Component {

methodToGrow(){}

anotherMethodToGrow(){}

methodToBeBundled(){}

render(){
return

...

}
}
```

**After applying grow-loader**

```js
class GrowablePage extends React.Component {
componentDidMount() {
if (this.grow) {
this.grow().then(() => {
this.hasGrown = true;
this.forceUpdate();
});
}
}
}

export default class A extends GrowablePage {
@grow
methodToGrow(){ }

@grow
anotherMethodToGrow(){ }

methodToBeBundled{ }

@grow
renderMore() {
return

...

}

render(){
return


{ this.hasGrown ? this.renderMore() : null }

}
}
```

## Background story
Higher-Order Components(HOC) is a common solution in implementing code-splitting. But we found HOC solutions unsuitable for our project built with React.js.

- We use different placeholder components for almost every page, but HOC solutions only support a common component for all pages.
- Instant page transition was our ultimate goal, but the following two problems had surfaced in using HOC solutions:
- We organize pages in a stack—[see our blog posting on this](https://engineering.linecorp.com/en/blog/detail/235)—the hooks provided could not be easily integrated.
- A lot of code modifications were required. Preloading pages would help our case, but preloading costs a lot in time and management. And page transition still felt janky for long pages because of DOM manipulation.

That's why we decided to split every page into two parts:

- **Basic part**: Contains placeholder components in the first view, which are to be included in the main bundle.
- **Grown part**: Parts to be dynamically imported, and rendered after the **Basic Part**

But manually splitting files requires a heavy workload and makes methods in both parts messy. This is why we created the `grow-loader` to do it in a flexible way.

## Contributing

Please check [CONTRIBUTING](./CONTRIBUTING.md) before making a contribution.

## License

[Apache License Version 2.0](./LICENSE)