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isEqual.js

Check if two objects or arrays are equal. Learn how it works.

/*!
 * Check if two objects or arrays are equal
 * (c) 2017 Chris Ferdinandi, MIT License, https://gomakethings.com
 * @param  {Object|Array}  value  The first object or array to compare
 * @param  {Object|Array}  other  The second object or array to compare
 * @return {Boolean}              Returns true if they're equal
 */
var isEqual = function (value, other) {

	// Get the value type
	var type = Object.prototype.toString.call(value);

	// If the two objects are not the same type, return false
	if (type !== Object.prototype.toString.call(other)) return false;

	// If items are not an object or array, return false
	if (['[object Array]', '[object Object]'].indexOf(type) < 0) return false;

	// Compare the length of the length of the two items
	var valueLen = type === '[object Array]' ? value.length : Object.keys(value).length;
	var otherLen = type === '[object Array]' ? other.length : Object.keys(other).length;
	if (valueLen !== otherLen) return false;

	// Compare two items
	var compare = function (item1, item2) {

		// Get the object type
		var itemType = Object.prototype.toString.call(item1);

		// If an object or array, compare recursively
		if (['[object Array]', '[object Object]'].indexOf(itemType) >= 0) {
			if (!isEqual(item1, item2)) return false;
		}

		// Otherwise, do a simple comparison
		else {

			// If the two items are not the same type, return false
			if (itemType !== Object.prototype.toString.call(item2)) return false;

			// Else if it's a function, convert to a string and compare
			// Otherwise, just compare
			if (itemType === '[object Function]') {
				if (item1.toString() !== item2.toString()) return false;
			} else {
				if (item1 !== item2) return false;
			}

		}
	};

	// Compare properties
	if (type === '[object Array]') {
		for (var i = 0; i < valueLen; i++) {
			if (compare(value[i], other[i]) === false) return false;
		}
	} else {
		for (var key in value) {
			if (value.hasOwnProperty(key)) {
				if (compare(value[key], other[key]) === false) return false;
			}
		}
	}

	// If nothing failed, return true
	return true;

};