json-stable-stringify

deterministic version of JSON.stringify() so you can get a consistent hash from stringified results

You can also pass in a custom comparison function.

example

const stringify = require('json-stable-stringify');

const 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

const stringify = require('json-stable-stringify')

const 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:

opts.cmp({ key: akey, value: avalue }, { key: bkey, value: bvalue }, { get(key): value })

For example, to sort on the object key names in reverse order you could write:

const stringify = require('json-stable-stringify');

const obj = { c: 8, b: [{ z: 6, y: 5, x: 4 },7], a: 3 };

const 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:

const stringify = require('json-stable-stringify');

const obj = { d: 6, c: 5, b: [{ z: 3, y: 2, x: 1 }, 9], a: 10 };

const 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}

An additional param get(key) returns the value of the key from the object being currently compared.

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:

const obj = { b: 1, a: { foo: 'bar', and: [1, 2, 3] } };

const 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.

install

With npm do:

npm install json-stable-stringify