estree-util-value-to-estree

Convert a JavaScript value to an ESTree expression.

Table of Contents

• Installation
• Usage
• API
  • valueToEstree(value, options?)
• Examples
  • Transform unsupported values into plain objects
  • Serialize custom values
• 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
• Float16Array
• Float32Array
• Float64Array
• Int8Array
• Int16Array
• Int32Array
• Map
• Number
• RegExp
• Set
• String
• Temporal.Duration
• Temporal.Instant
• Temporal.PlainDate
• Temporal.PlainDateTime
• Temporal.PlainYearMonth
• Temporal.PlainMonthDay
• Temporal.PlainTime
• Temporal.ZonedDateTime
• Uint8Array
• Uint8ClampedArray
• Uint16Array
• Uint32Array
• URL
• URLSearchParams
• custom

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

const result = valueToEstree({
  string: 'Hello world!',
  number: 42
})

console.log(result)
// {
//   type: 'ObjectExpression',
//   properties: [
//     {
//       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 }
//     }
//   ]
// })

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.
• replacer (Function) — A function to customize the serialization of a value. It accepts the value to serialize as an argument. It must return the value serialized to an ESTree expression. If nothing is returned, the value is processed by the builtin logic.

Examples

Transform unsupported values into plain objects

By default custom types result in an error. If options.instanceAsObject is set to true however, they are turned into plain objects.

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

class Point {
  line: number

  column: number

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

const point = new Point(2, 3)
const result = valueToEstree(point, { instanceAsObject: true })
console.log(result)
// {
//   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 }
//     }
//   ]
// }

Serialize custom values

You can customize the serialization of values using the replacer option. For example, to serialize a custom class:

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

class Point {
  line: number

  column: number

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

const point = new Point(2, 3)

const result = valueToEstree(point, {
  replacer(value) {
    if (value instanceof Point) {
      return {
        type: 'NewExpression',
        callee: { type: 'Identifier', name: 'Point' },
        arguments: [
          { type: 'Literal', value: value.line },
          { type: 'Literal', value: value.column }
        ]
      }
    }
  }
})
console.log(result)

Compatibility

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

License

MIT © Remco Haszing