Recursive Method to determine if two Object literals are deeply equal.

deep-equal.js

/**
 * Recursive function that compares two deeply nested objects to determine if they are identical in their structure and values.
 * 
 * @param {*} obj1 
 * @param {*} obj2 
 * @returns {boolean} Whether or not the two arguments being compared are deeply equal
 */
function deepEqual(obj1, obj2) {
    if (typeof obj1 !== typeof obj2) {
        return false;
    }

    /* FUNCTION */
    if (typeof obj1 === 'function') {
        /* Referential Equality or Identical Implementation */
        return (obj1 === obj2) || (obj1.toString() === obj2.toString());
    }

    /* ARRAY */
    if (Array.isArray(obj1) && !Array.isArray(obj2)) {
        return false;
    }
    if (Array.isArray(obj1) && obj1.length !== obj2.length) {
        return false;
    }
    if (Array.isArray(obj1)) {
        let sorted1 = obj1.sort();
        let sorted2 = obj2.sort();
        for (let i = 0; i < sorted1.length; i++) {
             if (!deepEqual(sorted1[i], sorted2[i])) {
                 return false
             }
        }
        return true;
    }
  
    /* DATE */
    if (obj1 instanceof Date && !obj2 instanceof Date) {
        return false;
    }
    if (obj1 instanceof Date) {
        return obj1.toString() === obj2.toString();
    }
  
    /* ERROR */
    if (obj1 instanceof Error && !obj2 instanceof Error) {
        return false;
    }
    if (obj1 instanceof Error) {
        return obj1.toString() === obj2.toString();
    }
  
    /* REGEXP */
    if (obj1 instanceof RegExp && !obj2 instanceof RegExp) {
        return false;
    }
    if (obj1 instanceof RegExp) {
        return obj1.toString() === obj2.toString();
    }

    /* SET */
    if (obj1 instanceof Set && !obj2 instanceof Set) {
        return false;
    }
    if (obj1 instanceof Set && obj1.size !== obj2.size) {
        return false;
    }
    if (obj1 instanceof Set) {
        let setEntries1 = Array.from(obj1).sort();
        let setEntries2 = Array.from(obj2).sort();
        for (let i = 0; i < setEntries1.length; i++) {
            if (!deepEqual(setEntries1[i], setEntries2[i])) {
                return false;
            }
        }
        return true;
    }

    /* MAP */
    if (obj1 instanceof Map && !obj2 instanceof Map) {
        return false;
    }
    if (obj1 instanceof Map && obj1.size !== obj2.size) {
        return false;
    }
    if (obj1 instanceof Map) {
        let mapEntries1 = Array.from(obj1).sort((a, b) => a[0] - b[0]);
        let mapEntries2 = Array.from(obj2).sort((a, b) => a[0] - b[0]);
        for (let i = 0; i < mapEntries1.length; i++) {
            if(!deepEqual(mapEntries1[i], mapEntries2[i])) {
                return false;
            }
        }
        return true;
    }

    /* NULL */
    if ((obj1 === null && obj2 !== null)
        || (obj1 !== null && obj2 === null)) {
        return false;
    }

    /* OBJECT */
    if (typeof obj1 === 'object' && Object.keys(obj1).length !== Object.keys(obj2).length) {
        return false;
    }
    if (typeof obj1 === 'object') {
        let objEntries1 = Object.entries(obj1);
        let objEntries2 = Object.entries(obj2);
        for (let i = 0; i < objEntries1.length; i++) {
            if (!deepEqual(objEntries1[i], objEntries2[i])) {
                return false;
            }
        }
        return true;
    }

    /* NaN */
    if ((Number.isNaN(obj1) && !Number.isNaN(obj2))
        || (!Number.isNaN(obj1) && Number.isNaN(obj2))) {
            return false
    }

    /* PRIMITIVES */
    return obj1 === obj2;
}

module.exports = { deepEqual }