flow-remove-types-no-whitespace
Version:
Removes Flow type annotations from JavaScript files with speed and simplicity.
191 lines (126 loc) • 4.16 kB
Markdown
flow-remove-types
=================
[](https://www.npmjs.com/package/flow-remove-types)
[](https://travis-ci.org/leebyron/flow-remove-types)
Turn your JavaScript with [Flow](https://flowtype.org/) type annotations into
standard JavaScript in an instant with no configuration and minimal setup.
[Flow](https://flowtype.org/) provides static type checking to JavaScript which
can both help find and detect bugs long before code is deployed and can make
code easier to read and more self-documenting. The Flow tool itself only reads
and analyzes code. Running code with Flow type annotations requires first
removing the annotations which are non-standard JavaScript. Typically this is
done via adding a plugin to your [Babel](https://babeljs.io/) configuration,
however Babel may be overkill if you're only targetting modern versions of
Node.js or just not using the modern ES2015 features that may not be in
every browser.
`flow-remove-types` is a faster, simpler, zero-configuration alternative with
minimal dependencies for super-fast `npm install` time.
## Get Started!
Use the command line:
```
npm install --global flow-remove-types
```
```
flow-remove-types --help
flow-remove-types input.js > output.js
```
Or the JavaScript API:
```
npm install flow-remove-types
```
```js
var flowRemoveTypes = require('flow-remove-types');
var fs = require('fs');
var input = fs.readFileSync('input.js', 'utf8');
var output = flowRemoveTypes(input);
fs.writeFileSync('output.js', output);
```
## Use in Build Systems:
**Rollup**: [`rollup-plugin-flow`](https://github.com/leebyron/rollup-plugin-flow)
**Browserify:** [`unflowify`](https://github.com/leebyron/unflowify)
## Use `flow-node`
Wherever you use `node` you can substitute `flow-node` and have a super fast
flow-types aware evaluator or REPL.
```
$ flow-node
> var x: number = 42
undefined
> x
42
```
## Use the require hook
Using the require hook allows you to automatically compile files on the fly when
requiring in node:
```js
require('flow-remove-types/register')
require('./some-module-with-flow-type-syntax')
```
## Dead-Simple Transforms
When `flow-remove-types` removes Flow types, it replaces them with whitespace.
This ensures that the transformed output has exactly the same number of lines
and characters and that all character offsets remain the same. This removes the
need for sourcemaps, maintains legible output, and ensures that it is super easy
to include `flow-remove-types` at any point in your existing build tools.
Built atop the excellent [`babylon`](https://github.com/babel/babylon) parser,
`flow-remove-types` shares the same parse rules as the source of truth as
Flow Babel plugins. It also passes through other common non-standard syntax such
as [JSX](https://facebook.github.io/jsx/) and experimental ECMAScript proposals.
**Before:**
```js
import SomeClass from 'some-module'
import type { SomeInterface } from 'some-module'
export class MyClass<T> extends SomeClass implements SomeInterface {
value: T
constructor(value: T) {
this.value = value
}
get(): T {
return this.value
}
}
```
**After:**
```js
import SomeClass from 'some-module'
export class MyClass extends SomeClass {
constructor(value ) {
this.value = value
}
get() {
return this.value
}
}
```
## Performance
### Install:
Installing via `npm` from an empty project:
**flow-remove-types:**
```
time npm install flow-remove-types
real 0m3.193s
user 0m1.643s
sys 0m0.775s
```
**Babel:**
```
time npm install babel-cli babel-plugin-transform-flow-strip-types
real 0m23.200s
user 0m10.395s
sys 0m4.238s
```
### Transform:
Transforming a directory of 20 files of 100 lines each:
**flow-remove-types:**
```
time flow-remove-types src/ --out-dir dest/
real 0m0.431s
user 0m0.436s
sys 0m0.068s
```
**Babel:**
```
time babel src/ --out-dir dest/
real 0m1.074s
user 0m1.092s
sys 0m0.149s
```