# json-stable-stringify <sup>[![Version Badge][npm-version-svg]][package-url]</sup>
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[![License][license-image]][license-url]
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[![npm badge][npm-badge-png]][package-url]
deterministic version of `JSON.stringify()` so you can get a consistent hash from stringified results
You can also pass in a custom comparison function.
[](https://ci.testling.com/ljharb/json-stable-stringify)
[](http://travis-ci.org/ljharb/json-stable-stringify)
# example
``` js
var stringify = require('json-stable-stringify');
var obj = { c: 8, b: [{ z: 6, y: 5, x: 4 }, 7], a: 3 };
console.log(stringify(obj));
```
output:
```
{"a":3,"b":[{"x":4,"y":5,"z":6},7],"c":8}
```
# methods
``` js
var stringify = require('json-stable-stringify')
```
## var str = stringify(obj, opts)
Return a deterministic stringified string `str` from the object `obj`.
## options
### cmp
If `opts` is given, you can supply an `opts.cmp` to have a custom comparison function for object keys.
Your function `opts.cmp` is called with these parameters:
``` js
opts.cmp({ key: akey, value: avalue }, { key: bkey, value: bvalue })
```
For example, to sort on the object key names in reverse order you could write:
``` js
var stringify = require('json-stable-stringify');
var obj = { c: 8, b: [{ z: 6, y: 5, x: 4 },7], a: 3 };
var s = stringify(obj, function (a, b) {
return b.key.localeCompare(a.key);
});
console.log(s);
```
which results in the output string:
```
{"c":8,"b":[{"z":6,"y":5,"x":4},7],"a":3}
```
Or if you wanted to sort on the object values in reverse order, you could write:
```
var stringify = require('json-stable-stringify');
var obj = { d: 6, c: 5, b: [{ z: 3, y: 2, x: 1 }, 9], a: 10 };
var s = stringify(obj, function (a, b) {
return a.value < b.value ? 1 : -1;
});
console.log(s);
```
which outputs:
```
{"d":6,"c":5,"b":[{"z":3,"y":2,"x":1},9],"a":10}
```
### space
If you specify `opts.space`, it will indent the output for pretty-printing.
Valid values are strings (e.g. `{space: \t}`) or a number of spaces
(`{space: 3}`).
For example:
```js
var obj = { b: 1, a: { foo: 'bar', and: [1, 2, 3] } };
var s = stringify(obj, { space: ' ' });
console.log(s);
```
which outputs:
```
{
"a": {
"and": [
1,
2,
3
],
"foo": "bar"
},
"b": 1
}
```
### replacer
The replacer parameter is a function `opts.replacer(key, value)` that behaves the same as the replacer
[from the core JSON object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Using_native_JSON#The_replacer_parameter).
# install
With [npm](https://npmjs.org) do:
```
npm install json-stable-stringify
```
# license
MIT
[package-url]: https://npmjs.org/package/json-stable-stringify
[npm-version-svg]: https://versionbadg.es/ljharb/json-stable-stringify.svg
[deps-svg]: https://david-dm.org/ljharb/json-stable-stringify.svg
[deps-url]: https://david-dm.org/ljharb/json-stable-stringify
[dev-deps-svg]: https://david-dm.org/ljharb/json-stable-stringify/dev-status.svg
[dev-deps-url]: https://david-dm.org/ljharb/json-stable-stringify#info=devDependencies
[npm-badge-png]: https://nodei.co/npm/json-stable-stringify.png?downloads=true&stars=true
[license-image]: https://img.shields.io/npm/l/json-stable-stringify.svg
[license-url]: LICENSE
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[downloads-url]: https://npm-stat.com/charts.html?package=json-stable-stringify
[codecov-image]: https://codecov.io/gh/ljharb/json-stable-stringify/branch/main/graphs/badge.svg
[codecov-url]: https://app.codecov.io/gh/ljharb/json-stable-stringify/
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