pretty-format
Advanced tools
Package description
The pretty-format npm package is a JavaScript library that allows you to serialize any JavaScript value into a string with a human-readable format. It is particularly useful for snapshot testing, where you want to compare the expected and actual output of your test cases.
Pretty-printing of basic JavaScript types
This feature allows you to convert basic JavaScript types like objects, arrays, strings, numbers, etc., into a nicely formatted string.
const prettyFormat = require('pretty-format');
const value = { foo: 'bar', baz: 42 };
console.log(prettyFormat(value));Customizing output with plugins
pretty-format supports plugins that can be used to customize the output for specific types of values, such as React elements.
const prettyFormat = require('pretty-format');
const ReactElementPlugin = require('pretty-format/plugins/ReactElement');
const reactElement = <div>Hello World</div>;
console.log(prettyFormat(reactElement, { plugins: [ReactElementPlugin] }));Minimizing diff output
By using pretty-format in combination with a diffing library like jest-diff, you can minimize the output of diffs to make them easier to read and understand.
const prettyFormat = require('pretty-format');
const diff = require('jest-diff');
const oldValue = { a: 'old', b: 'values' };
const newValue = { a: 'new', b: 'values' };
const difference = diff(prettyFormat(oldValue), prettyFormat(newValue));
console.log(difference);Chalk is a popular npm package for styling terminal strings. While it doesn't serialize objects, it can be used in conjunction with pretty-format to colorize the output, enhancing readability.
Util is a core Node.js module that provides a method called 'inspect' for printing objects in a readable format. It is similar to pretty-format but is built into Node.js and does not support plugins.
js-beautify is an npm package that can format HTML, CSS, and JavaScript code. It is more focused on formatting code rather than serializing arbitrary JavaScript values like pretty-format.
Changelog
jest 22.0.0
[jest-resolve] Use module.builtinModules as BUILTIN_MODULES when it exists[jest-worker] Remove debug and inspect flags from the arguments sent to the child (#5068)[jest-config] Use all --testPathPattern and <regexForTestFiles> args in testPathPattern (#5066)[jest-cli] Do not support --watch inside non-version-controlled environments (#5060)[jest-config] Escape Windows path separator in testPathPattern CLI arguments (#5054)[jest-jasmine] Register sourcemaps as node environment to improve performance with jsdom (#5045)[pretty-format] Do not call toJSON recursively (#5044)[pretty-format] Fix errors when identity-obj-proxy mocks CSS Modules (#4935)[babel-jest] Fix support for namespaced babel version 7 (#4918)[expect] fix .toThrow for promises (#4884)[jest-docblock] pragmas should preserve urls (#4837)[jest-cli] Check if npm_lifecycle_script calls Jest directly (#4629)[jest-cli] Fix --showConfig to show all configs (#4494)[jest-cli] Throw if maxWorkers doesn't have a value (#4591)[jest-cli] Use fs.realpathSync.native if available (#5031)[jest-config] Fix --passWithNoTests (#4639)[jest-config] Support rootDir tag in testEnvironment (#4579)[jest-editor-support] Fix --showConfig to support jest 20 and jest 21 (#4575)[jest-editor-support] Fix editor support test for node 4 (#4640)[jest-mock] Support mocking constructor in mockImplementationOnce (#4599)[jest-runtime] Fix manual user mocks not working with custom resolver (#4489)[jest-util] Fix runOnlyPendingTimers for setTimeout inside setImmediate (#4608)[jest-message-util] Always remove node internals from stacktraces (#4695)[jest-resolve] changes method of determining builtin modules to include missing builtins (#4740)[pretty-format] Prevent error in pretty-format for window in jsdom test env (#4750)[jest-resolve] Preserve module identity for symlinks (#4761)[jest-config] Include error message for preset json (#4766)[pretty-format] Throw PrettyFormatPluginError if a plugin halts with an exception (#4787)[expect] Keep the stack trace unchanged when PrettyFormatPluginError is thrown by pretty-format (#4787)[jest-environment-jsdom] Fix asynchronous test will fail due to timeout issue. (#4669)[jest-cli] Fix --onlyChanged path case sensitivity on Windows platform (#4730)[jest-runtime] Use realpath to match transformers (#5000)[expect] [BREAKING] Replace identity equality with Object.is in toBe matcher (#4917)[jest-message-util] Add codeframe to test assertion failures (#5087)[jest-config] Add Global Setup/Teardown options (#4716)[jest-config] Add testEnvironmentOptions to apply to jsdom options or node context. (#5003)[jest-jasmine2] Update Timeout error message to jest.timeout and display current timeout value (#4990)[jest-runner] Enable experimental detection of leaked contexts (#4895)[jest-cli] Add combined coverage threshold for directories. (#4885)[jest-mock] Add timestamps to mock state. (#4866)[eslint-plugin-jest] Add prefer-to-have-length lint rule. (#4771)[jest-environment-jsdom] [BREAKING] Upgrade to JSDOM@11 (#4770)[jest-environment-*] [BREAKING] Add Async Test Environment APIs, dispose is now teardown (#4506)[jest-cli] Add an option to clear the cache (#4430)[babel-plugin-jest-hoist] Improve error message, that the second argument of jest.mock must be an inline function (#4593)[jest-snapshot] [BREAKING] Concatenate name of test and snapshot (#4460)[jest-cli] [BREAKING] Fail if no tests are found (#3672)[jest-diff] Highlight only last of odd length leading spaces (#4558)[jest-docblock] Add docblock.print() (#4517)[jest-docblock] Add strip (#4571)[jest-docblock] Preserve leading whitespace in docblock comments (#4576)[jest-docblock] remove leading newlines from parswWithComments().comments (#4610)[jest-editor-support] Add Snapshots metadata (#4570)[jest-editor-support] Adds an 'any' to the typedef for updateFileWithJestStatus (#4636)[jest-editor-support] Better monorepo support (#4572)[jest-environment-jsdom] Add simple rAF polyfill in jsdom environment to work with React 16 (#4568)[jest-environment-node] Implement node Timer api (#4622)[jest-jasmine2] Add testPath to reporter callbacks (#4594)[jest-mock] Added support for naming mocked functions with .mockName(value) and .mockGetName() (#4586)[jest-runtime] Add module.loaded, and make module.require not enumerable (#4623)[jest-runtime] Add module.parent (#4614)[jest-runtime] Support sourcemaps in transformers (#3458)[jest-snapshot] [BREAKING] Add a serializer for jest.fn to allow a snapshot of a jest mock (#4668)[jest-worker] Initial version of parallel worker abstraction, say hello! (#4497)[jest-jasmine2] Add testLocationInResults flag to add location information per spec to test results (#4782)[jest-environment-jsdom] Update JSOM to 11.4, which includes built-in support for requestAnimationFrame (#4919)[jest-cli] Hide watch usage output when running on non-interactive environments (#4958)[jest-snapshot] Promises support for toThrowErrorMatchingSnapshot (#4946)[jest-cli] Explain which snapshots are obsolete (#5005)[docs] Add guide of using with puppeteer (#5093)[jest-util] jest-util should not depend on jest-mock (#4992)[*] [BREAKING] Drop support for Node.js version 4 (#4769)[docs] Wrap code comments at 80 characters (#4781)[eslint-plugin-jest] Removed from the Jest core repo, and moved to https://github.com/jest-community/eslint-plugin-jest (#4867)[babel-jest] Explicitly bump istanbul to newer versions (#4616)[expect] Upgrade mocha and rollup for browser testing (#4642)[docs] Add info about coveragePathIgnorePatterns (#4602)[docs] Add Vuejs series of testing with Jest (#4648)[docs] Mention about optional done argument in test function (#4556)[jest-cli] Bump node-notifier version (#4609)[jest-diff] Simplify highlight for leading and trailing spaces (#4553)[jest-get-type] Add support for date (#4621)[jest-matcher-utils] Call chalk.inverse for trailing spaces (#4578)[jest-runtime] Add .advanceTimersByTime; keep .runTimersToTime() as an alias.[docs] Include missing dependency in TestEnvironment sample code[docs] Add clarification for hook execution order[docs] Update expect.anything() sample code (#5007)Readme
Stringify any JavaScript value.
$ npm install pretty-format
var prettyFormat = require('pretty-format');
var obj = { foo: 1 };
obj.self = obj;
obj[Symbol('foo')] = 'foo';
obj.bar = new Map();
obj.bar.set('baz', 'bat');
console.log(prettyFormat(obj));
// Object {
// "foo": 1,
// "self": [Circular],
// "bar": Map {
// "baz" => "bat"
// },
// Symbol(foo): "foo"
// }
FAQs
Stringify any JavaScript value.
The npm package pretty-format receives a total of 66,623,110 weekly downloads. As such, pretty-format popularity was classified as popular.
We found that pretty-format demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 3 open source maintainers collaborating on the project.
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