estree-util-value-to-estree

Convert a JavaScript value to an ESTree expression.

Table of Contents

• Installation
• Usage
• API
  • valueToEstree(value, options?)
• Compatibility
• License

Installation

npm install estree-util-value-to-estree

Usage

This package converts a JavaScript value to an ESTree expression for values that can be constructed without the need for a context.

Currently the following types are supported:

• bigint
• boolean
• null
• number (Including Infinity and NaN)
• string
• symbol (shared and well-known)
• object
• null-prototype Object
• undefined
• Array
• BigInt64Array
• BigUint64Array
• Boolean
• Buffer
• Date
• Float32Array
• Float64Array
• Int16Array
• Int32Array
• Int8Array
• Map
• Number
• RegExp
• Set
• String
• Uint16Array
• Uint32Array
• Uint8Array
• Uint8ClampedArray
• URL
• URLSearchParams

If options.instanceAsObject is set to true, other objects are turned into plain object.

import assert from 'node:assert/strict'

import { valueToEstree } from 'estree-util-value-to-estree'

const result = valueToEstree({
  null: null,
  undefined,
  string: 'Hello world!',
  number: 42,
  negativeNumber: -1337,
  infinity: Number.POSITIVE_INFINITY,
  notANumber: Number.NaN,
  regex: /\w+/i,
  date: new Date('1970-01-01'),
  array: ['I’m an array item!'],
  object: { nested: 'value' }
})

assert.deepEqual(result, {
  type: 'ObjectExpression',
  properties: [
    {
      type: 'Property',
      method: false,
      shorthand: false,
      computed: false,
      kind: 'init',
      key: { type: 'Literal', value: 'null' },
      value: { type: 'Literal', value: null }
    },
    {
      type: 'Property',
      method: false,
      shorthand: false,
      computed: false,
      kind: 'init',
      key: { type: 'Literal', value: 'undefined' },
      value: { type: 'Identifier', name: 'undefined' }
    },
    {
      type: 'Property',
      method: false,
      shorthand: false,
      computed: false,
      kind: 'init',
      key: { type: 'Literal', value: 'string' },
      value: { type: 'Literal', value: 'Hello world!' }
    },
    {
      type: 'Property',
      method: false,
      shorthand: false,
      computed: false,
      kind: 'init',
      key: { type: 'Literal', value: 'number' },
      value: { type: 'Literal', value: 42 }
    },
    {
      type: 'Property',
      method: false,
      shorthand: false,
      computed: false,
      kind: 'init',
      key: { type: 'Literal', value: 'negativeNumber' },
      value: {
        type: 'UnaryExpression',
        operator: '-',
        prefix: true,
        argument: { type: 'Literal', value: 1337 }
      }
    },
    {
      type: 'Property',
      method: false,
      shorthand: false,
      computed: false,
      kind: 'init',
      key: { type: 'Literal', value: 'infinity' },
      value: { type: 'Identifier', name: 'Infinity' }
    },
    {
      type: 'Property',
      method: false,
      shorthand: false,
      computed: false,
      kind: 'init',
      key: { type: 'Literal', value: 'notANumber' },
      value: { type: 'Identifier', name: 'NaN' }
    },
    {
      type: 'Property',
      method: false,
      shorthand: false,
      computed: false,
      kind: 'init',
      key: { type: 'Literal', value: 'regex' },
      value: {
        type: 'Literal',
        value: /\w+/i,
        regex: { pattern: '\\w+', flags: 'i' }
      }
    },
    {
      type: 'Property',
      method: false,
      shorthand: false,
      computed: false,
      kind: 'init',
      key: { type: 'Literal', value: 'date' },
      value: {
        type: 'NewExpression',
        callee: { type: 'Identifier', name: 'Date' },
        arguments: [{ type: 'Literal', value: 0 }]
      }
    },
    {
      type: 'Property',
      method: false,
      shorthand: false,
      computed: false,
      kind: 'init',
      key: { type: 'Literal', value: 'array' },
      value: {
        type: 'ArrayExpression',
        elements: [{ type: 'Literal', value: 'I’m an array item!' }]
      }
    },
    {
      type: 'Property',
      method: false,
      shorthand: false,
      computed: false,
      kind: 'init',
      key: { type: 'Literal', value: 'object' },
      value: {
        type: 'ObjectExpression',
        properties: [
          {
            type: 'Property',
            method: false,
            shorthand: false,
            computed: false,
            kind: 'init',
            key: { type: 'Literal', value: 'nested' },
            value: { type: 'Literal', value: 'value' }
          }
        ]
      }
    }
  ]
})

class Point {
  line: number

  column: number

  constructor(line: number, column: number) {
    this.line = line
    this.column = column
  }
}

// Normally complex objects throw.
assert.throws(() => valueToEstree(new Point(2, 3)))

// `instanceAsObject: true` treats them as plain objects.
assert.deepEqual(valueToEstree(new Point(2, 3), { instanceAsObject: true }), {
  type: 'ObjectExpression',
  properties: [
    {
      type: 'Property',
      method: false,
      shorthand: false,
      computed: false,
      kind: 'init',
      key: { type: 'Literal', value: 'line' },
      value: { type: 'Literal', value: 2 }
    },
    {
      type: 'Property',
      method: false,
      shorthand: false,
      computed: false,
      kind: 'init',
      key: { type: 'Literal', value: 'column' },
      value: { type: 'Literal', value: 3 }
    }
  ]
})

API

This API exports the function valueToEstree.

valueToEstree(value, options?)

Convert a value to an ESTree node.

options

• instanceAsObject (boolean, default: false) — If true, treat objects that have a prototype as plain objects.
• preserveReferences (boolean, default: false) — If true, preserve references to the same object found within the input. This also allows to serialize recursive structures. If needed, the resulting expression will be an iife.

Compatibility

This project is compatible with Node.js 16 or greater.

License

MIT © Remco Haszing