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

$ yarn add pretty-format

Usage

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

const 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:

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

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

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

ReactTestComponent and ReactElement plugins

const prettyFormat = require('pretty-format');
const reactTestPlugin = require('pretty-format').plugins.ReactTestComponent;
const reactElementPlugin = require('pretty-format').plugins.ReactElement;

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

const element = React.createElement('h1', null, 'Hello World');

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