@ava/pretty-format

Stringify any JavaScript value.

• Supports all built-in JavaScript types
• Blazingly fast (similar performance to v8's JSON.stringify and significantly faster than Node's util.format)
• Plugin system for extending with custom types (i.e. ReactTestComponent)

Installation

$ npm install @ava/pretty-format

Usage

var prettyFormat = require('pretty-format');

var obj = { property: {} };
obj.circularReference = obj;
obj[Symbol('foo')] = 'foo';
obj.map = new Map();
obj.map.set('prop', 'value');
obj.array = [1, NaN, Infinity];

console.log(prettyFormat(obj));

Result:

Object {
  "property": Object {},
  "circularReference": [Circular],
  "map": Map {
    "prop" => "value"
  },
  "array": Array [
    1,
    NaN,
    Infinity
  ],
  Symbol(foo): "foo"
}

Type Support

Object, Array, ArrayBuffer, DataView, Float32Array, Float64Array, Int8Array, Int16Array, Int32Array, Uint8Array, Uint8ClampedArray, Uint16Array, Uint32Array, arguments, Boolean, Date, Error, Function, Infinity, Map, NaN, null, Number, RegExp, Set, String, Symbol, undefined, WeakMap, WeakSet

API

console.log(prettyFormat(object));
console.log(prettyFormat(object, options));

Options:

• callToJSON Type: boolean, default: true Call toJSON() on passed object.
• indent Type: number, default: 2 Number of spaces for indentation.
• maxDepth Type: number, default: Infinity Print only this number of levels.
• min Type: boolean, default: false Print without whitespace.
• plugins Type: array, default: [] Plugins (see the next section).
• printFunctionName Type: boolean, default: true Print function names or just [Function].
• escapeRegex Type: boolean, default: false Escape special characters in regular expressions.
• highlight Type: boolean, default: false Highlight syntax for terminal (works only with ReactTestComponent and ReactElement plugins.
• theme Type: object, default: {tag: 'cyan', content: 'reset'...} Syntax highlight theme. Uses ansi-styles colors + reset for no color. Available types: tag, content, prop and value.

Plugins

Pretty format also supports adding plugins:

var fooPlugin = {
  test: function(val) {
    return val && val.hasOwnProperty('foo');
  },
  print: function(val, print, indent) {
    return 'Foo: ' + print(val.foo);
  }
};

var obj = { foo: { bar: {} } };

prettyFormat(obj, {
  plugins: [fooPlugin]
});
// Foo: Object {
//   "bar": Object {}
// }

ReactTestComponent and ReactElement plugins

var prettyFormat = require('pretty-format');
var reactTestPlugin = require('pretty-format/plugins/ReactTestComponent');
var reactElementPlugin = require('pretty-format/plugins/ReactElement');

var React = require('react');
var renderer = require('react-test-renderer');

var jsx = React.createElement('h1', null, 'Hello World');

prettyFormat(renderer.create(jsx).toJSON(), {
  plugins: [reactTestPlugin, reactElementPlugin]
});
// <h1>
//   Hello World
// </h1>