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https://github.com/cpojer/js-codemod

Codemod scripts to transform code to next generation JS
https://github.com/cpojer/js-codemod

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Codemod scripts to transform code to next generation JS

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## js-codemod [![Build Status](https://travis-ci.org/cpojer/js-codemod.svg)](https://travis-ci.org/cpojer/js-codemod)



This repository contains a collection of codemod scripts for use with

[JSCodeshift](https://github.com/facebook/jscodeshift).



### Setup & Run



```sh

npm install -g jscodeshift

git clone https://github.com/cpojer/js-codemod.git

jscodeshift -t  

```



Use the `-d` option for a dry-run and use `-p` to print the output for

comparison.



### Included Scripts



#### `arrow-function-arguments`



```sh

jscodeshift -t js-codemod/transforms/arrow-function-arguments.js 

```



#### `arrow-function`



Transforms callbacks only when it can guarantee it won't break `this` context in the function. Also transforms `function() { }.bind(this)` calls to `() => {}`.



```sh

jscodeshift -t js-codemod/transforms/arrow-function.js 

```



##### Options:



`--inline-single-expressions=true`: If you are feeling lucky and you know that returning the value of single-expression functions will not affect the behavior of your application you can specify the option and it will transform `function() { relay(); }` to `() => relay()` instead of `() => { relay(); }`.



`--max-width=120`: Try the best it can to keep line lengths under the specified length.



#### `invalid-requires`



```sh

jscodeshift -t js-codemod/transforms/invalid-requires.js 

```



#### `jest-update`



```sh

jscodeshift -t js-codemod/transforms/jest-update.js 

```



#### `no-reassign-params`



Converts functions to not reassign to parameters. This is useful to turn on in conjunction with [Flow's const_params](https://flow.org/en/docs/config/options/#toc-experimental-const-params-boolean) option.



```sh

jscodeshift -t js-codemod/transforms/no-reassign-params.js 

```



#### `no-vars`



Conservatively converts `var` to `const` or `let`.



```sh

jscodeshift -t js-codemod/transforms/no-vars.js 

```



#### `object-shorthand`



Transforms object literals to use [ES6 shorthand](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer#New_notations_in_ECMAScript_2015)

for properties and methods.



```sh

jscodeshift -t js-codemod/transforms/object-shorthand.js 

```



#### `outline-require`



```sh

jscodeshift -t js-codemod/transforms/outline-require.js 

```



#### `rm-copyProperties`



```sh

jscodeshift -t js-codemod/transforms/rm-copyProperties.js 

```



#### `rm-merge`



```sh

jscodeshift -t js-codemod/transforms/rm-merge.js 

```



#### `rm-object-assign`



```sh

jscodeshift -t js-codemod/transforms/rm-object-assign.js 

```



#### `rm-requires`



Removes any requires where the imported value is not referenced. Additionally

if any module is required more than once the two requires will be merged.



```sh

jscodeshift -t js-codemod/transforms/rm-requires.js 

```



#### `template-literals`



Replaces string concatenation with template literals.



```sh

jscodeshift -t js-codemod/transforms/template-literals.js 

```



Adapted from ["How to write a codemod" by Ramana Venkata](https://vramana.github.io/blog/2015/12/21/codemod-tutorial/).



Areas of improvement:



- Comments in the middle of string concatenation are currently added before the

  string but after the assignment. Perhaps in these situations, the string

  concatenation should be preserved as-is.



- Nested concatenation inside template literals is not currently simplified.

  Currently, a + `b${'c' + d}` becomes `${a}b${'c' + d}` but it would ideally

  become ``${a}b${`c${d}`}``.



- Unnecessary escaping of quotes from the resulting template literals is

  currently not removed. This is possibly the domain of a different transform.



- Unicode escape sequences are converted to unicode characters when the

  simplified concatenation results in a string literal instead of a template

  literal. It would be nice to perserve the original--whether it be a unicode

  escape sequence or a unicode character.



#### `touchable`



```sh

jscodeshift -t js-codemod/transforms/touchable.js 

```



#### `trailing-commas`



Adds trailing commas to array and object literals.



```sh

jscodeshift -t js-codemod/transforms/trailing-commas.js 

```



#### `unchain-variables`



Unchains chained variable declarations.



```sh

jscodeshift -t js-codemod/transforms/unchain-variables.js 

```



#### `underscore-to-lodash-native`



Replaces underscore (or lodash) to ES6 + lodash, preferring native ES6 array methods. Member imports are used by default to allow tree-shaking, but the `--split-imports=true` option will split each lodash import into its own `lodash/` import.



```sh

jscodeshift -t js-codemod/transforms/underscore-to-lodash-native.js 

```



#### `unquote-properties`



Removes quotes from object properties whose keys are strings which are valid

identifiers.



```sh

jscodeshift -t js-codemod/transforms/unquote-properties.js 

```



#### `updated-computed-props`



```sh

jscodeshift -t js-codemod/transforms/updated-computed-props.js 

```



#### `use-strict`



Adds a top-level `'use strict'` statement to JavaScript files



```sh

jscodeshift -t js-codemod/transforms/use-strict.js 

```



### Included extensions



`jscodeshift-imports` helpers for modifying `import` and `require` statements,

[see docs](extensions/imports/).



### Recast Options



[Options to recast's printer](https://github.com/benjamn/recast/blob/master/lib/options.ts) can be provided

through the `printOptions` command line argument



```sh

jscodeshift -t transform.js  --printOptions='{"quote":"double"}'

```