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Safely serialize a value to JSON without unintended loss of data or going into an infinite loop due to circular references.


The native JSON.stringify function drops or silently modifies all values that are not supported by the JSON specification:

JSON.stringify({ a: 42, b: undefined })
// returns '{"a":42}'

// returns null

JSON.stringify([1, NaN, 3])
// returns '[1,null,3]'

In many cases this is not the behaviour you want: relying on the serialization method to clean up your data is error prone and can lead to subtle bugs that are annoying to find. json-strictify helps you to easily avoid these issues with literally a single line of code.

Unlike json-stringify-safe it does not attempt to "fix" its input but always bails out when it encounters something that would prevent it from being serialized properly.


Simply install via npm:

npm install json-strictify


json-strictify exposes three methods: stringify, parse and enable, so it can be used as a drop-in replacement for the native JSON object:

import JSON from 'json-strictify'


The parse method is simply a reference to the native JSON.parse function.


The stringify function throws an error if the input to be serialized contains invalid values:

import JSONs from 'json-strictify'

JSONs.stringify({ x: 42, y: NaN })
// InvalidValueError: Invalid value at /y (NaN is not JSON-serializable)

Also, if the data you want to stringify contains circular references a CircularReferenceError is thrown:

const data = []
// CircularReferenceError: Circular reference found at "/0"

The location of the value that caused the error is given as a JSON Pointer reference.

ESLint integration

If you want to ensure that all serialization is done through json-strictify you can disable the global JSON variable like so:

"globals": {
    "JSON": "off"

See the ESLint documentation on configuring globals for details.

Disabling json-strictify

In production you may not want to have the additional overhead introduced by json-strictify. This can easily be avoided by calling the enabled method:

import JSONs from 'json-strictify'
const JSON = JSONs.enabled(config.debug)

// or for older versions of Javascript:
const JSON = require('json-strictify').enabled(config.debug)

If called with a falsy parameter, enabled will return an object that delegates directly to the native JSON object so there will be no performance penalty whatsoever.

Note: json-strictify is disabled by default if NODE_ENV is set to production (you may still enable it manually, of course).


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