shallowequal

What is shallowequal?

The shallowequal npm package is a simple utility for performing shallow equality checks on objects or values. It is primarily used to compare the values of two objects to determine if they are equivalent in terms of their direct properties, without deeply traversing any nested objects. This can be particularly useful in optimizations where a deep equality check is unnecessary or too costly in terms of performance.

What are shallowequal's main functionalities?

Shallow Equality Check for Objects

This feature allows you to compare two objects to see if they have the same top-level properties with the same values, without checking for deep equality.

const shallowequal = require('shallowequal');
const obj1 = { a: 1, b: 2 };
const obj2 = { a: 1, b: 2 };
const areEqual = shallowequal(obj1, obj2); // true

Shallow Equality Check with Custom Comparer

This feature allows you to perform a shallow equality check between two objects, but with a custom comparison function for the values, enabling more flexible comparisons.

const shallowequal = require('shallowequal');
const obj1 = { a: 1, b: '2' };
const obj2 = { a: 1, b: 2 };
const areEqual = shallowequal(obj1, obj2, (val1, val2) => String(val1) === String(val2)); // true

Other packages similar to shallowequal

lodash.isequal

Lodash's isEqual method provides deep equality comparison, unlike shallowequal which only performs shallow comparisons. This makes lodash.isequal more suitable for scenarios where nested object properties need to be compared.

fast-deep-equal

fast-deep-equal is another npm package that offers deep equality checks, similar to lodash.isequal but optimized for speed. It contrasts with shallowequal by providing deep comparison capabilities, which can be more comprehensive but potentially slower for simple use cases.

react-fast-compare

react-fast-compare is designed specifically for comparing React props and state objects efficiently. It performs deep equality checks and is optimized for React's use cases, making it different from shallowequal which only offers shallow comparison.

README

shallowequal

shallowequal is like lodash's isEqualWith but for shallow (strict) equal.

shallowequal(value, other, [customizer], [thisArg])

Performs a shallow equality comparison between two values (i.e. value and other) to determine if they are equivalent.

The equality is performed by iterating through keys on the given value, and returning false whenever any key has values which are not strictly equal between value and other. Otherwise, return true whenever the values of all keys are strictly equal.

If customizer (expected to be a function) is provided it is invoked to compare values. If customizer returns undefined (i.e. void 0), then comparisons are handled by the shallowequal function instead.

The customizer is bound to thisArg and invoked with three arguments: (value, other, key).

NOTE: Docs are (shamelessly) adapted from lodash's docs

Usage

$ npm install --save shallowequal
$ yarn add shallowequal

const shallowequal = require('shallowequal');

const object = { 'user': 'fred' };
const other = { 'user': 'fred' };

object == other;
// → false

shallowequal(object, other);
// → true

Credit

Code for shallowEqual originated from https://github.com/gaearon/react-pure-render/ and has since been refactored to have the exact same API as lodash.isEqualWith (as of v4.17.4).

Development

• node.js and npm. See: https://github.com/creationix/nvm#installation
• yarn. See: https://yarnpkg.com/en/docs/install
• npm dependencies. Run: yarn install

Chores

• Lint: yarn run lint
• Test: yarn run test
• Pre-publish: yarn run prepublish

License

MIT.