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https://github.com/ull-esit-pl/compact-js-ast

Outputs a compact string representation of the espree AST of an input program.
https://github.com/ull-esit-pl/compact-js-ast

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Outputs a compact string representation of the espree AST of an input program.

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README 

        
## Synopsis



Outputs a compact string representation of the espree AST of an input program. It provides an executable `compast` that can be used to output 

a summarized version of the AST of a given JavaScript program. The output can be in YML or JSON format. The program can be given as a file or as a string in the command line.



```

$ compast -h                    

Usage: compast [options] [filename]



Converts a JS program into a JSON or YML AST format



Arguments:

  filename                    file with the original code



Options:

  -V, --version               output the version number

  -o, --output      file name of the json output program

  -p, --program   JS program is given in the command line

  -jw --whites        string '  ' Specifies the number of whites for formatting the object (default: "  ")

  -e --hide    List of AST fields to omit (default: [])

  -f --hideFile     File with a line per AST fields to omit

  -j --json                   output in JSON format (default is YML

  -n --no-parse               do not parse the code, assume the input is already an AST in json format

  -b --babel                  parse the code with babel (default is espree)

  -a --all                    output all fields

  -l --location               omit only location fields

  -h, --help                  display help for command

```



## Install



```

npm i -g compact-js-ast

```



## Examples



Here is an example of the YML output of the AST for the program `a.b(4)`:



```yml

$ compast -p 'a.b(4)'           

type: "Program"

body:

  - type: "ExpressionStatement"

    expression:

      type: "CallExpression"

      callee:

        type: "MemberExpression"

        object:

          type: "Identifier"

          name: "a"

        property:

          type: "Identifier"

          name: "b"

      arguments:

        - type: "Literal"

          value: 4

```



```

$ compast -jp 'a.b(4)'

```

```json

{

  "type": "Program",

  "body": [

    {

      "type": "ExpressionStatement",

      "expression": {

        "type": "CallExpression",

        "callee": {

          "type": "MemberExpression",

          "object": {

            "type": "Identifier",

            "name": "a"

          },

          "property": {

            "type": "Identifier",

            "name": "b"

          }

        },

        "arguments": [

          {

            "type": "Literal",

            "value": 4

          }

        ]

      }

    }

  ]

}

```

Same, but removing `names`s and `value`s:



```yml

$ compast -e name value -p 'a.b(4)' 

type: "Program"

body:

  - type: "ExpressionStatement"

    expression:

      type: "CallExpression"

      callee:

        type: "MemberExpression"

        object:

          type: "Identifier"

        property:

          type: "Identifier"

      arguments:

        - type: "Literal"

```



Using babel:



`➜  nicolo-howto-talk git:(main) compast -blp 'a?.[0]' | yq '.program.body[0]'`

```json

{

  "type": "ExpressionStatement",

  "expression": {

    "type": "OptionalMemberExpression",

    "object": {

      "type": "Identifier",

      "name": "a"

    },

    "computed": true,

    "property": {

      "type": "NumericLiteral",

      "extra": {

        "rawValue": 0,

        "raw": "0"

      },

      "value": 0

    },

    "optional": true

  }

}

```



## See also



- [astexplorer.net](https://astexplorer.net/) is a web-based tool for exploring the AST of a JavaScript program. It provides a visual representation of the AST and allows to explore the different nodes and their properties.

- [jq](https://stedolan.github.io/jq/) is a lightweight and flexible command-line JSON processor. It can be used to filter and transform the output of `compast` to obtain a more compact representation of the AST.

- [yq](https://github.com/mikefarah/yq) is a YAML version of jq

- [jless](https://www.npmjs.com/package/less) is a command-line JSON viewer that can be used to visualize the output of `compast` in a more readable format.