---
title: Introduction
---

import { Steps, LinkCard, Card, CardGrid } from '@astrojs/starlight/components';

`jscodeshift` is a toolkit for building and running codemods over multiple JavaScript or TypeScript files. It provides:

- A runner, which executes the provided transform for each file passed to it. It also outputs a summary of how many files have **not** been transformed.
- A wrapper around [recast](https://github.com/benjamn/recast), providing a different API.  Recast is an AST-to-AST transform tool and also tries to preserve the style of original code
as much as possible.

## How does jscodeshift work?

<Steps>
  1. **Parsing Code into AST**

      First, jscodeshift takes your JavaScript code and converts it into an Abstract Syntax Tree (AST). An AST is a tree representation of your code where each node represents a different part of the code, like variables, functions, and expressions.
  
  2. **Transforming the AST**
      
      Using jscodeshift, you can navigate through the AST and apply transformations. For example, you can find all instances of a certain function and rename it or change its parameters.
  
  3. **Generating Code from AST**
      
      After transforming the AST, jscodeshift converts it back into JavaScript code. The result is your original code with the specified changes applied.
</Steps>

## Installation

Get jscodeshift from [npm](https://www.npmjs.com/package/jscodeshift):

```
$ npm install -g jscodeshift
```

This will install the runner as `jscodeshift`.


## Getting started

<CardGrid>
  <LinkCard title="Build jscodeshift codemods" href="/build/api-reference/" />
  <LinkCard title="Run jscodeshift codemods" href="/run/cli/" />
</CardGrid>