gistfile1.txt

var MAX_DEPTH_OF_CHECK = 6;

    function objectsAreEqual(first, second, depthOfCheck) {
        var isFirstObject = isObject(first);
        var isSecondObject = isObject(second);
        if (!isFirstObject && !isSecondObject) { // both are not objects, compare primitives
            return first === second;
        } else if (!isFirstObject || !isSecondObject) { // one of them is not object
            return false;
        }
        if (depthOfCheck >= MAX_DEPTH_OF_CHECK) { // do not check object up to infinite loop
            return false;
        } else {
            depthOfCheck++;
        }
        var compareFunctions = false;
        if (isFunction(first)) {
            if (!isFunction(second)) { // one is function, another is object
                return false;
            }
            compareFunctions = true;
        }
        var firstProps = Object.keys(first);
        var secondProps = Object.keys(second);
        if (firstProps.length !== secondProps.length) { // not equal amount of properties
            return false;
        }
        if (!firstProps.length) { // empty objects, nothing to compare
            return true;
        }
        var diffProps = firstProps.filter(function (val) {
            return secondProps.indexOf(val) < 0;
        });
        if (diffProps.length) {
            return false; // names of props are not equal
        }
        firstProps = firstProps.sort(function (a, b) {
            return convertTypeToWeight(first[b]) - convertTypeToWeight(first[a]);
        });
        for (var i = 0, len = firstProps.length; i < len; i++) {
            var key = firstProps[i];
            var firstItem = first[key];
            var secondItem = second[key];
            var objectsEqual = objectsAreEqual(firstItem, secondItem, depthOfCheck);
            if (!objectsEqual) {
                return false;
            }
        }
        if (compareFunctions) {
            if (first.name === second.name) { // functions are equal by name
                return true;
            } else {
                return first.toString() === second.toString();  // functions are equal by code
            }
        }
        return true;
    }

    function shouldComponentUpdate(nextProps, nextState) {
        var depthOfCheck = 0;
        try {
            var statesAreEqual = objectsAreEqual(this.state, nextState, depthOfCheck);
            var propsAreEqual = objectsAreEqual(this.props, nextProps, depthOfCheck);
            var shouldUpdate = !statesAreEqual || !propsAreEqual;
            return shouldUpdate;
        } catch (e) {
            return true;
        }
    }