# fast-json-stable-stringify Deterministic `JSON.stringify()` - a faster version of [@substack](https://github.com/substack)'s json-stable-strigify without [jsonify](https://github.com/substack/jsonify). You can also pass in a custom comparison function. [](https://travis-ci.org/epoberezkin/fast-json-stable-stringify) [](https://coveralls.io/github/epoberezkin/fast-json-stable-stringify?branch=master) # example ``` js var stringify = require('fast-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('fast-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('fast-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('fast-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} ``` ### cycles Pass `true` in `opts.cycles` to stringify circular property as `__cycle__` - the result will not be a valid JSON string in this case. TypeError will be thrown in case of circular object without this option. # install With [npm](https://npmjs.org) do: ``` npm install fast-json-stable-stringify ``` # benchmark To run benchmark (requires Node.js 6+): ``` node benchmark ``` Results: ``` fast-json-stable-stringify x 17,189 ops/sec ±1.43% (83 runs sampled) json-stable-stringify x 13,634 ops/sec ±1.39% (85 runs sampled) fast-stable-stringify x 20,212 ops/sec ±1.20% (84 runs sampled) faster-stable-stringify x 15,549 ops/sec ±1.12% (84 runs sampled) The fastest is fast-stable-stringify ``` # license [MIT](https://github.com/epoberezkin/fast-json-stable-stringify/blob/master/LICENSE)