fast-safe-stringify
Safe and fast serialization alternative to JSON.stringify.
Gracefully handles circular structures instead of throwing.
Provides a deterministic ("stable") version as well that will also gracefully
handle circular structures. See the example below for further information.
Usage
The same as JSON.stringify.
stringify(value[, replacer[, space]])
const safeStringify = require('fast-safe-stringify')
const o = { a: 1 }
o.o = o
console.log(safeStringify(o))
// '{"a":1,"o":"[Circular]"}'
console.log(JSON.stringify(o))
// TypeError: Converting circular structure to JSON
function replacer(key, value) {
console.log('Key:', JSON.stringify(key), 'Value:', JSON.stringify(value))
// Remove the circular structure
if (value === '[Circular]') {
return
}
return value
}
const serialized = safeStringify(o, replacer, 2)
// Key: "" Value: {"a":1,"o":"[Circular]"}
// Key: "a" Value: 1
// Key: "o" Value: "[Circular]"
console.log(serialized)
// {
// "a": 1
// }
Using the deterministic version also works the same:
const safeStringify = require('fast-safe-stringify')
const o = { b: 1, a: 0 }
o.o = o
console.log(safeStringify(o))
// '{"b":1,"a":0,"o":"[Circular]"}'
console.log(safeStringify.stableStringify(o))
// '{"a":0,"b":1,"o":"[Circular]"}'
console.log(JSON.stringify(o))
// TypeError: Converting circular structure to JSON
A faster and side-effect free implementation is available in the
[safe-stable-stringify][] module. However it is still considered experimental
due to a new and more complex implementation.
Differences to JSON.stringify
In general the behavior is identical to JSON.stringify. The replacer
and space options are also available.
A few exceptions exist to JSON.stringify while using toJSON or
replacer:
Regular safe stringify
-
Manipulating a circular structure of the passed in value in a
toJSONor the
replaceris not possible! It is possible for any other value and property. -
In case a circular structure is detected and the
replaceris used it
will receive the string[Circular]as the argument instead of the circular
object itself.
Deterministic ("stable") safe stringify
-
Manipulating the input object either in a
toJSONor thereplacer
function will not have any effect on the output. The output entirely relies on
the shape the input value had at the point passed to the stringify function! -
In case a circular structure is detected and the
replaceris used it
will receive the string[Circular]as the argument instead of the circular
object itself.
A side effect free variation without these limitations can be found as well
(safe-stable-stringify). It is also faster than the current
implementation. It is still considered experimental due to a new and more
complex implementation.
Benchmarks
Although not JSON, the Node.js util.inspect method can be used for similar
purposes (e.g. logging) and also handles circular references.
Here we compare fast-safe-stringify with some alternatives:
(Lenovo T450s with a i7-5600U CPU using Node.js 8.9.4)
fast-safe-stringify: simple object x 1,121,497 ops/sec ±0.75% (97 runs sampled)
fast-safe-stringify: circular x 560,126 ops/sec ±0.64% (96 runs sampled)
fast-safe-stringify: deep x 32,472 ops/sec ±0.57% (95 runs sampled)
fast-safe-stringify: deep circular x 32,513 ops/sec ±0.80% (92 runs sampled)
util.inspect: simple object x 272,837 ops/sec ±1.48% (90 runs sampled)
util.inspect: circular x 116,896 ops/sec ±1.19% (95 runs sampled)
util.inspect: deep x 19,382 ops/sec ±0.66% (92 runs sampled)
util.inspect: deep circular x 18,717 ops/sec ±0.63% (96 runs sampled)
json-stringify-safe: simple object x 233,621 ops/sec ±0.97% (94 runs sampled)
json-stringify-safe: circular x 110,409 ops/sec ±1.85% (95 runs sampled)
json-stringify-safe: deep x 8,705 ops/sec ±0.87% (96 runs sampled)
json-stringify-safe: deep circular x 8,336 ops/sec ±2.20% (93 runs sampled)
For stable stringify comparisons, see the performance benchmarks in the
safe-stable-stringify readme.
Protip
Whether fast-safe-stringify or alternatives are used: if the use case
consists of deeply nested objects without circular references the following
pattern will give best results.
Shallow or one level nested objects on the other hand will slow down with it.
It is entirely dependant on the use case.
const stringify = require('fast-safe-stringify')
function tryJSONStringify (obj) {
try { return JSON.stringify(obj) } catch (_) {}
}
const serializedString = tryJSONStringify(deep), stringify(deep)
Acknowledgements
Sponsored by nearForm
License
MIT