isEq.js

'use strict';

/**
 * ↘️↘️
 * @author Muthu Kumar <https://mkr.pw>
 * isEq(item1, item2 [, compareKeys])
 * @description Deep compares objects or arrays and returns boolean.
 * Supports Number, String, Boolean, Regexp, Objects, Arrays
 * @param {*} item1 - Object or Array to compare against.
 * @param {*} item2 - Object or Array to compare with.
 * @param {Array} [compareKeys] - Keys to compare against. Ignores other keys.
 */

const isEq = (item1, item2, compareKeys) => {

	// Simple compare:
	// If item1 and item2 are strictly equal, will
	// pass all tests regardless of compare keys.
	if(item1 === item2) return true;

	// Returns false if different types are used.
	if (typeof item1 !== typeof item2) return false;

	// Arrays are of type object, hence let's go one further step
	// to prove type inequality
	if ((Array.isArray(item1)
		&& !Array.isArray(item2))
		|| ((Array.isArray(item2)
		&& !Array.isArray(item1))))
		return false;

	// 'NaN's are special. They aren't equal to each other.
	if (typeof item1 === 'number') {
		if(isNaN(item1) && isNaN(item2)) return false;
		else return item1 === item2;
	};

	// Since types are already equal, let's find if items are equal.
	if ((typeof item1 === 'string') ||
		(typeof item1 === 'boolean') ||
		(item1 === null) ||
		(item1 === undefined)) {
		return (item1 === item2);
	};

	// Regexp needs to be Stringified first before comparing equality
	if (item1 instanceof RegExp) return String(item1) === String(item2);

	// If none of the above conditions returned, then check if inputs are handlable
	// If they're not, fall back to strict equality
	if (typeof (item1) !== 'object' || typeof (item2) !== 'object')
		return (item1 === item2);

	const item1Keys = Object.keys(item1);
	const item2Keys = Object.keys(item2);

	// If compare keys array is not given, let's check length of props
	// and check second array against first.
	if (!compareKeys) {
		compareKeys = item1Keys;
		if (item1Keys.length !== item2Keys.length) {
			return false;
		};
	};

	if(!(Array.isArray(compareKeys)))
		throw new Error('[isEq] third parameter should be an array of keys!');

	// Either both are empty objects or arrays, or compareArray is empty. Return true.
	if(compareKeys.length === 0) return true;

	// For each key in our reference...
	for (let KeyIndex in compareKeys) {

		let Key = compareKeys[KeyIndex];
		if (Array.isArray(item1[Key]) && Array.isArray(item2[Key])) {
			Key = KeyIndex;
		};

		// Inequality at this point can be because it's just comparing
		// two objects or arrays that may or may not be equivalent.
		if (item1[Key] !== item2[Key]) {
			if (typeof (item1[Key] === 'object') && typeof (item2[Key] === 'object') ||
				(Array.isArray(item1[Key]) && Array.isArray(item2[Key]))) {
				if (!isEq(item1[Key], item2[Key])) {
					return false;
				};
			} else {
				return false;
			};
		};
	};

	return true;
};

module.exports = isEq;