Estree-util-value-to-estree NPM

estree-util-value-to-estree

Convert a JavaScript value to an ESTree expression.

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:

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.