js-codemod 
This repository contains a collection of codemod scripts for use with JSCodeshift.
Setup & Run
npm install -g jscodeshift
git clone https://github.com/cpojer/js-codemod.git
jscodeshift -t <codemod-script> <file>Use the -d option for a dry-run and use -p to print the output for
comparison.
Included Scripts
arrow-function-arguments
jscodeshift -t js-codemod/transforms/arrow-function-arguments.js <file>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 () => {}.
jscodeshift -t js-codemod/transforms/arrow-function.js <file>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
jscodeshift -t js-codemod/transforms/invalid-requires.js <file>jest-update
jscodeshift -t js-codemod/transforms/jest-update.js <file>no-reassign-params
Converts functions to not reassign to parameters. This is useful to turn on in conjunction with Flow's const_params option.
jscodeshift -t js-codemod/transforms/no-reassign-params.js <file>no-vars
Conservatively converts var to const or let.
jscodeshift -t js-codemod/transforms/no-vars.js <file>object-shorthand
Transforms object literals to use ES6 shorthand for properties and methods.
jscodeshift -t js-codemod/transforms/object-shorthand.js <file>outline-require
jscodeshift -t js-codemod/transforms/outline-require.js <file>rm-copyProperties
jscodeshift -t js-codemod/transforms/rm-copyProperties.js <file>rm-merge
jscodeshift -t js-codemod/transforms/rm-merge.js <file>rm-object-assign
jscodeshift -t js-codemod/transforms/rm-object-assign.js <file>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.
jscodeshift -t js-codemod/transforms/rm-requires.js <file>template-literals
Replaces string concatenation with template literals.
jscodeshift -t js-codemod/transforms/template-literals.js <file>Adapted from "How to write a codemod" by Ramana Venkata.
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
jscodeshift -t js-codemod/transforms/touchable.js <file>trailing-commas
Adds trailing commas to array and object literals.
jscodeshift -t js-codemod/transforms/trailing-commas.js <file>unchain-variables
Unchains chained variable declarations.
jscodeshift -t js-codemod/transforms/unchain-variables.js <file>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/<method> import.
jscodeshift -t js-codemod/transforms/underscore-to-lodash-native.js <file>unquote-properties
Removes quotes from object properties whose keys are strings which are valid identifiers.
jscodeshift -t js-codemod/transforms/unquote-properties.js <file>updated-computed-props
jscodeshift -t js-codemod/transforms/updated-computed-props.js <file>use-strict
Adds a top-level 'use strict' statement to JavaScript files
jscodeshift -t js-codemod/transforms/use-strict.js <file>Included extensions
jscodeshift-imports helpers for modifying import and require statements,
see docs.
Recast Options
Options to recast's printer can be provided
through the printOptions command line argument
jscodeshift -t transform.js <file> --printOptions='{"quote":"double"}'