json5-writer

Comment-preserving JSON / JSON5 parser

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

Example

1const json5Writer = require('json5-writer')
2const config = fs.readFileSync('config.json5', 'utf-8')
3const writer = json5Writer.load(config)
4writer.write({
5  'eat honey': { cooldown: 3 },
6  speak: { cooldown: 2 },
7  bear: { actions: ['eat honey', 'speak'] },
8})
9fs.writeFileSync('config.json5', writer.toSource(), 'utf-8')

config.json5 diff

1 {
2   // actions
3   'eat honey': {
4-    cooldown: 4,
5+    cooldown: 3,
6   },
7+
8+  'speak': {
9+    cooldown: 2,
10+  },
11
12   // Note: A day without a friend is like a pot without a single drop of honey left inside.
13
14   // entities
15   'bear':  {
16-    actions: [ 'eat honey' ],
17-    canSpeak: true,
18+    actions: ['eat honey', 'speak'],
19   },
20 }

Installation

1npm install --save json5-writer

Usage

1const writerInstance = json5Writer.load(jsonStr) // get a writer instance for the given JSON / JSON5 string
2writerInstance.write(objectOrArray) // update jsonStr, preserving comments
3const ast = writerInstance.ast // directly access the AST with jscodeshift API
4const newJson5 = writerInstance.toSource(options) // get the modified JSON5 string
5const newJson = writerInstance.toJSON(options) // get the modified JSON string

.write(value)

Updates the JSON / JSON5 string with the new value. Any field or property that doesn't exist in value is removed.

To keep an existing value, use undefined:

1const writer = json5Writer.load(`[{ name: 'Noah' }, { name: 'Nancy' }]`)
2writer.write([{ name: undefined, age: 28 }, undefined ])
3write.toSource() // [{ name: 'Noah', age: 28 }, { name: 'Nancy' }]

.ast

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

1const j = require('jscodeshift')
2const writer = json5Writer.load('[1, 2, 3, 4]')
3writer.ast.find(j.Literal).forEach(path => {
4  if (path.value.value % 2 === 0) path.value.value = 0
5})
6write.toSource() // [1, 0, 3, 0]

.toSource(options)

Get the modified JSON5 string. Alias for .toJSON5().

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

1.toSource({ quote: 'single', trailingComma: true, quoteKeys: undefined })

• quoteKeys controls whether object keys are quoted. It can have three different values:
  • false - no object keys will have quotes
  • true - all object keys will have quotes
  • undefined - object key quote usage is inferred [default]
• quote can be either single or double

View the remaining options here.

.toJSON(options)

Same as .toSource(options) but with quote: 'double', trailingComma: false, quoteKeys: true by default.