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');

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:

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/build/plugins/ReactTestComponent');
const reactElementPlugin = require('pretty-format/build/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>

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