json5-writer

Comment-preserving JSON5 parser

json5-writer provides an API for parsing JSON5 without losing comments or formatting. It does so by transforming JSON5 into a JavaScript AST and using jscodeshift to update values.

Example

const json5Writer = require('json5-writer')
const config = fs.readFileSync('config.json5', 'utf-8')
const writer = json5Writer.load(config)
writer.write({
  'eat honey': { cooldown: 3 },
  speak: { cooldown: 2 },
  bear: { actions: ['eat honey', 'speak'] },
})
fs.writeFileSync('config.json5', writer.toSource(), 'utf-8')

config.json5 diff

 {
   // actions
   'eat honey': {
-    cooldown: 4,
+    cooldown: 3,
   },
+
+  'speak': {
+    cooldown: 2,
+  },

   // Note: A day without a friend is like a pot without a single drop of honey left inside.

   // entities
   'bear':  {
-    actions: [ 'eat honey' ],
-    canSpeak: true,
+    actions: ['eat honey', 'speak'],
   },
 }

Installation

npm install --save json5-writer

Usage

const writerInstance = json5Writer.load(json) // get a writer instance for the given JSON5 string
writerInstance.write(value) // write an object or array to JSON5
const ast = writerInstance.ast // directly access the AST with jscodeshift API
const newJson = writerInstance.toSource(options) // get the modified JSON5 string

.write(value)

Writes an object or array to JSON5. Any field or property that doesn't exist in value is removed.

To keep an existing value, use undefined:

const writer = json5Writer.load(`[{ name: 'Noah' }, { name: 'Nancy' }]`)
writer.write([{ name: undefined, age: 28 }, undefined ])
write.toSource() // [{ name: 'Noah', age: 28 }, { name: 'Nancy' }]

.ast

Directly access the JSON5-turned-JavaScript AST, wrapped in the jscodeshift API.

const j = require('jscodeshift')
const writer = json5Writer.load('[1, 2, 3, 4]')
writer.ast.find(j.Literal).forEach(path => {
  if (path.value.value % 2 === 0) path.value.value = 0
})
write.toSource() // [1, 0, 3, 0]

.toSource(options)

Get the modified JSON5 string.

options control what is output. By default, single quotes and trailing commas are enabled.

.toSource({quote: 'double'}) // sets modified strings to use double quotes

See the list of options here.

Limitations

• Doesn't support writing a single primitive value: .write('primitive')
• Doesn't support characters or syntax that are valid in JSON5 but not valid in JavaScript