flow-node
v2.245.2
Published
Removes Flow type annotations from JavaScript files with speed and simplicity.
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17,203
Readme
flow-remove-types
Turn your JavaScript with Flow type annotations into standard JavaScript in an instant with no configuration and minimal setup.
Flow 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 configuration, however Babel may be overkill if you're only targeting 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.
Getting 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
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.toString());
When using the flow-remove-types
script, be sure not to direct the output to itself!
Use in Build Systems
Rollup: rollup-plugin-flow
Browserify: unflowify
Webpack: remove-flow-types-loader
Gulp: gulp-flow-remove-types
Use with existing development tools
ESLint: eslint-plugin-flowtype
Mocha:
mocha -r flow-remove-types/register
Jest: Add to your config:
transform: { "^.+\\.js(?:\\.flow)?$": "flow-remove-types/jest" }
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
Note: This package is also available under the alias
flow-node
since it's often looked for at that location due to the popularity of this script. Both scripts are available no matter which package you install.
Use the require hook
Using the require hook allows you to automatically compile files on the fly when requiring in node, useful during development:
require('flow-remove-types/register')
require('./some-module-with-flow-type-syntax')
You can also provide options to the require hook:
// Transforms all files, not just those with a "@flow" comment.
require('flow-remove-types/register')({ all: true })
Use options to define exactly which files to includes
or excludes
with regular
expressions. All files are included by default except those found in the
node_modules
folder, which is excluded by default.
require('flow-remove-types/register')({ includes: /\/custom_path\// })
Don't use the require hook in packages distributed on NPM As always, don't forget to use
flow-remove-types
to compile files before distributing your code on npm, as using the require hook affects the whole runtime and not just your module and may hurt the runtime performance of code that includes it.
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 official Flow parser,
flow-remove-types
is designed to operate on the same syntax Flow itself understands.
It also passes through other common non-standard syntax such as JSX
and experimental ECMAScript proposals that Flow supports.
Before:
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:
import SomeClass from 'some-module'
export class MyClass extends SomeClass {
constructor(value ) {
this.value = value
}
get() {
return this.value
}
}
Pretty Transform
Rather not have the whitespace? Pass the --pretty
flag to remove the whitespace.
flow-remove-types --pretty --sourcemaps source.js
Or using the JS API:
var flowRemoveTypes = require('flow-remove-types');
var fs = require('fs');
var input = fs.readFileSync('input.js', 'utf8');
var output = flowRemoveTypes(input, { pretty: true });
fs.writeFileSync('output.js', output.toString());
var sourceMap = output.generateMap();
fs.writeFileSync('output.js.map', JSON.stringify(sourceMap));
Performance
NOTE: These timings are for
flow-remove-types
v1.
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