equals.js

const isArray = Array.isArray;
const toString = Object.prototype.toString;

function isDate(value) {
    return toString.call(value) === '[object Date]';
}

function isRegExp(value) {
  return toString.call(value) === '[object RegExp]';
}

function equals(v1, v2) {
    if (v1 === v2) return true;
    if (v1 !== v1 && v2 !== v2) return true; // NaN

    let t1 = typeof v1, t2 = typeof v2;

    if (t1 === t2 && t1 === 'object') {
        if (isArray(v1)) {
            if (!isArray(v2)) return false;
            if (v1.length === v2.length) {
                return v1.every((item, index) => {
                    return equals(item, v2[index]);
                });
            }
        } else if(isDate(v1)) {
            if (!isDate(v2)) return false;
            return +v1 === +v2;
        } else if(isRegExp(v1)) {
            if (!isRegExp(v2)) return false;
            return v1.toString() === v2.toString();
        } else {
            for (let k in v1) {
                let vv1 = v1[k], vv2 = v2[k];

                if (!equals(vv1, vv2)) return false;
            }

            return true;
        }
    }

    return false;
}