⛑️ JSON serialization should never fail.
Features
Prevent JSON.stringify() from:
- Throwing
- Changing types
- Filtering or transforming values unexpectedly
Example
import safeJsonValue from 'safe-json-value'
const input = { one: true }
input.self = input
JSON.stringify(input) // Throws due to cycle
const { value, changes } = safeJsonValue(input)
JSON.stringify(value) // '{"one":true}"
console.log(changes) // List of changed properties
// [
// {
// path: ['self'],
// oldValue: <ref *1> { one: true, self: [Circular *1] },
// newValue: undefined,
// reason: 'unsafeCycle'
// }
// ]Install
npm install safe-json-valueThis package works in both Node.js >=16.17.0 and browsers.
This is an ES module. It must be loaded using
an import or import() statement,
not require(). If TypeScript is used, it must be configured to
output ES modules,
not CommonJS.
API
safeJsonValue(value, options?)
value any
options Options?
Return value: object
Makes value JSON-safe by:
- Omitting properties which would throw,
change type unexpectedly or
be filtered with
JSON.stringify() - Resolving properties which would change value with
JSON.stringify()
This never throws.
Options
Object with the following properties.
maxSize
Type: number
Default: 1e7
Big JSON strings can make a process, filesystem operation or network request
crash. maxSize prevents it by setting a maximum
JSON.stringify(value).length.
Additional properties beyond the size limit are omitted. They are completely removed, not truncated (including strings).
const input = { one: true, two: 'a'.repeat(1e6) }
JSON.stringify(safeJsonValue(input, { maxSize: 1e5 }).value) // '{"one":true}"shallow
Type: boolean
Default: false
If false, object/array properties are processed recursively. Please note that
cycles are not removed when this is true.
Return value
Object with the following properties.
value
Type: any
Copy of the input value after applying all the changes to make
it JSON-safe.
The top-level value itself might be changed (including to undefined) if it
is either invalid JSON or has a toJSON() method.
The value is not serialized to a JSON string. This allows choosing the
serialization format (JSON, YAML, etc.), processing the value, etc.
changes
Type: Change[]
List of changes applied to value. Each item is an
individual change to a specific property. A given property might have multiple
changes, listed in order.
changes[*].path
Type: Array<string | symbol | number>
Property path.
changes[*].oldValue
Type: any
Property value before the change.
changes[*].newValue
Type: any
Property value after the change. undefined means the property was omitted.
changes[*].reason
Type: string
Reason for the change among:
- Exceptions:
"unsafeCycle","unsafeBigInt","unsafeSize","unsafeException","unsafeToJSON","unsafeGetter" - Invalid descriptors:
"descriptorNotWritable","descriptorNotConfigurable" - Unexpected types:
"unstableInfinite" - Filtered values:
"ignoredFunction","ignoredUndefined","ignoredSymbolValue","ignoredSymbolKey","ignoredNotEnumerable","ignoredArrayProperty" - Unresolved values:
"unresolvedToJSON","unresolvedClass","unresolvedGetter"
changes[*].error
Type: Error?
Error that triggered the change. Only present if reason is
"unsafeException",
"unsafeToJSON" or
"unsafeGetter".
Changes
This is a list of all possible changes applied to make the value JSON-safe.
Exceptions
JSON.stringify() can throw on specific properties. Those are omitted.
Cycles
const input = { one: true }
input.self = input
JSON.stringify(input) // Throws due to cycle
JSON.stringify(safeJsonValue(input).value) // '{"one":true}"Infinite recursion
const input = { toJSON: () => ({ one: true, input }) }
JSON.stringify(input) // Throws due to infinite `toJSON()` recursion
JSON.stringify(safeJsonValue(input).value) // '{"one":true,"input":{...}}"BigInt
const input = { one: true, two: 0n }
JSON.stringify(input) // Throws due to BigInt
JSON.stringify(safeJsonValue(input).value) // '{"one":true}"Big output
const input = { one: true, two: '\n'.repeat(5e8) }
JSON.stringify(input) // Throws due to max string length
JSON.stringify(safeJsonValue(input).value) // '{"one":true}"Exceptions in toJSON()
const input = {
one: true,
two: {
toJSON: () => {
throw new Error('example')
},
},
}
JSON.stringify(input) // Throws due to `toJSON()`
JSON.stringify(safeJsonValue(input).value) // '{"one":true}"Exceptions in getters
const input = {
one: true,
get two() {
throw new Error('example')
},
}
JSON.stringify(input) // Throws due to `get two()`
JSON.stringify(safeJsonValue(input).value) // '{"one":true}"Exceptions in proxies
const input = new Proxy(
{ one: false },
{
get: () => {
throw new Error('example')
},
},
)
JSON.stringify(input) // Throws due to proxy
JSON.stringify(safeJsonValue(input).value) // '{}'Invalid descriptors
Non-writable properties
const input = {}
Object.defineProperty(input, 'one', {
value: true,
enumerable: true,
writable: false,
configurable: true,
})
input.one = false // Throws: non-writable
const safeInput = safeJsonValue(input).value
safeInput.one = false // Does not throw: now writableNon-configurable properties
const input = {}
Object.defineProperty(input, 'one', {
value: true,
enumerable: true,
writable: true,
configurable: false,
})
// Throws: non-configurable
Object.defineProperty(input, 'one', { value: false, enumerable: false })
const safeInput = safeJsonValue(input).value
// Does not throw: now configurable
Object.defineProperty(safeInput, 'one', { value: false, enumerable: false })Unexpected types
JSON.stringify() changes the types of specific values unexpectedly. Those are
omitted.
NaN and Infinity
const input = { one: true, two: Number.NaN, three: Number.POSITIVE_INFINITY }
JSON.stringify(input) // '{"one":true,"two":null,"three":null}"
JSON.stringify(safeJsonValue(input).value) // '{"one":true}"Invalid array items
const input = [true, undefined, Symbol(), false]
JSON.stringify(input) // '[true, null, null, false]'
JSON.stringify(safeJsonValue(input).value) // '[true, false]'Filtered values
JSON.stringify() omits some specific types. Those are omitted right away to
prevent any unexpected output.
Functions
const input = { one: true, two: () => {} }
JSON.parse(JSON.stringify(input)) // { one: true }
safeJsonValue(input).value // { one: true }undefined
const input = { one: true, two: undefined }
JSON.parse(JSON.stringify(input)) // { one: true }
safeJsonValue(input).value // { one: true }Symbol values
const input = { one: true, two: Symbol() }
JSON.parse(JSON.stringify(input)) // { one: true }
safeJsonValue(input).value // { one: true }Symbol keys
const input = { one: true, [Symbol()]: true }
JSON.parse(JSON.stringify(input)) // { one: true }
safeJsonValue(input).value // { one: true }Non-enumerable keys
const input = { one: true }
Object.defineProperty(input, 'two', { value: true, enumerable: false })
JSON.parse(JSON.stringify(input)) // { one: true }
safeJsonValue(input).value // { one: true }Array properties
const input = [true]
input.prop = true
JSON.parse(JSON.stringify(input)) // [true]
safeJsonValue(input).value // [true]Unresolved values
JSON.stringify() can transform some values. Those are resolved right away to
prevent any unexpected output.
toJSON()
const input = {
toJSON: () => ({ one: true }),
}
JSON.parse(JSON.stringify(input)) // { one: true }
safeJsonValue(input).value // { one: true }Dates
const input = { one: new Date() }
JSON.parse(JSON.stringify(input)) // { one: '2022-07-29T14:37:40.865Z' }
safeJsonValue(input).value // { one: '2022-07-29T14:37:40.865Z' }Classes
const input = { one: new Set([]) }
JSON.parse(JSON.stringify(input)) // { one: {} }
safeJsonValue(input).value // { one: {} }Getters
const input = {
get one() {
return true
},
}
JSON.parse(JSON.stringify(input)) // { one: true }
safeJsonValue(input).value // { one: true }Proxies
const input = new Proxy(
{ one: false },
{
get: () => true,
},
)
JSON.parse(JSON.stringify(input)) // { one: true }
safeJsonValue(input).value // { one: true }Related projects
is-json-value: Check if a value is valid JSONtruncate-json: Truncate a JSON stringguess-json-indent: Guess the indentation of a JSON stringerror-serializer: Convert errors to/from plain objects
Support
For any question, don't hesitate to submit an issue on GitHub.
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Contributing
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 ehmicky 💻 🎨 🤔 📖 |
 Pedro Augusto de Paula Barbosa 📖 |