jsonld-stable-stringify/readme.markdown

deterministic JSON.stringify() with custom sorting to get deterministic hashes from stringified JSON-LD

# jsonld-stable-stringify

Deterministic version of `JSON.stringify()` so you can get a consistent hash
from stringified JSON-LD. This is a clone of [json-stable-stringify](https://github.com/substack/json-stable-stringify) except
that arrays are sorted too (since JSON-LD arrays are interpreted as sets, so
order does not matter). The [`@list`](https://www.w3.org/TR/json-ld11/#lists) keyword: arrays marked as lists are not sorted (and this applies recursively).

You can also pass in a custom comparison function.

[![Build Status](https://travis-ci.com/periodo/jsonld-stable-stringify.svg?branch=master)](https://travis-ci.com/periodo/jsonld-stable-stringify)

# examples

``` js
var stringify = require('jsonld-stable-stringify');
var obj = { c: 8, b: [{z:6,y:5,x:4},7], a: 3 };
console.log(stringify(obj));
```

output:

```
{"a":3,"b":[7,{"x":4,"y":5,"z":6}],"c":8}
```

``` js
var stringify = require('jsonld-stable-stringify');
var obj = {'@context':{a:{"@container": "@list"}}, a:[[3,2,1],[6,5,4]]};
console.log(stringify(obj));
```

output:

```
{"@context":{"a":{"@container":"@list"}},"a":[[3,2,1],[6,5,4]]}
```

# 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 a.key < b.key ? 1 : -1;
});
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 jsonld-stable-stringify
```

# license

MIT