esprima: JavaScrip Syntax Tree

In js: Tools for Working with JavaScript in R

Description

Esprima is a high performance, standard-compliant ECMAScript parser. It has full support for ECMAScript 2017 and returns a sensible syntax tree format as standardized by ESTree project.

Usage

esprima_tokenize(text, range = FALSE, loc = FALSE, comment = FALSE)

esprima_parse(text, jsx = FALSE, range = FALSE, loc = FALSE,
  tolerant = FALSE, tokens = FALSE, comment = FALSE)

Arguments

text	a character vector with JavaScript code
range	Annotate each token with its zero-based start and end location
loc	Annotate each token with its column and row-based location
comment	Include every line and block comment in the output
jsx	Support JSX syntax
tolerant	Tolerate a few cases of syntax errors
tokens	Collect every token

Details

The esprima_tokenize function returns a data frame with JavaScript tokens. The esprima_parse function returns the Syntax Tree in JSON format. This can be parsed to R using e.g. jsonlite::fromJSON.

References

Esprima documentation: http://esprima.readthedocs.io/en/4.0/.

Examples

code <- "function test(x, y){ x = x || 1; y = y || 1; return x*y;}"
esprima_tokenize(code)
esprima_parse(code)

Example output

         type    value
1     Keyword function
2  Identifier     test
3  Punctuator        (
4  Identifier        x
5  Punctuator        ,
6  Identifier        y
7  Punctuator        )
8  Punctuator        {
9  Identifier        x
10 Punctuator        =
11 Identifier        x
12 Punctuator       ||
13    Numeric        1
14 Punctuator        ;
15 Identifier        y
16 Punctuator        =
17 Identifier        y
18 Punctuator       ||
19    Numeric        1
20 Punctuator        ;
21    Keyword   return
22 Identifier        x
23 Punctuator        *
24 Identifier        y
25 Punctuator        ;
26 Punctuator        }
{
  "type": "Program",
  "body": [
    {
      "type": "FunctionDeclaration",
      "id": {
        "type": "Identifier",
        "name": "test"
      },
      "params": [
        {
          "type": "Identifier",
          "name": "x"
        },
        {
          "type": "Identifier",
          "name": "y"
        }
      ],
      "body": {
        "type": "BlockStatement",
        "body": [
          {
            "type": "ExpressionStatement",
            "expression": {
              "type": "AssignmentExpression",
              "operator": "=",
              "left": {
                "type": "Identifier",
                "name": "x"
              },
              "right": {
                "type": "LogicalExpression",
                "operator": "||",
                "left": {
                  "type": "Identifier",
                  "name": "x"
                },
                "right": {
                  "type": "Literal",
                  "value": 1,
                  "raw": "1"
                }
              }
            }
          },
          {
            "type": "ExpressionStatement",
            "expression": {
              "type": "AssignmentExpression",
              "operator": "=",
              "left": {
                "type": "Identifier",
                "name": "y"
              },
              "right": {
                "type": "LogicalExpression",
                "operator": "||",
                "left": {
                  "type": "Identifier",
                  "name": "y"
                },
                "right": {
                  "type": "Literal",
                  "value": 1,
                  "raw": "1"
                }
              }
            }
          },
          {
            "type": "ReturnStatement",
            "argument": {
              "type": "BinaryExpression",
              "operator": "*",
              "left": {
                "type": "Identifier",
                "name": "x"
              },
              "right": {
                "type": "Identifier",
                "name": "y"
              }
            }
          }
        ]
      },
      "generator": false,
      "expression": false,
      "async": false
    }
  ],
  "sourceType": "script"
} 

js documentation built on July 2, 2020, 2:47 a.m.