Passing unit tests

app.js

module.exports = {
    nestedTypeFilter: function(inputObject, typeSpec) {
        //Immediately passes basic filter tests
        //Runs through chain of filters otherwise
        if ((typeof typeSpec == 'function') && (typeof inputObject != 'object')) {
            return basicFilter(inputObject, typeSpec);
        } else {
            return cycleFilter(inputObject, typeSpec);
        }

        //A way to organize the process
        function cycleFilter(input, spec) {
            if (checkArrays(input, spec) == false) {
                return checkObjects(input, spec)
            } else {
                return checkArrays(input, spec)
            }
            
        }
        
        //Needed to determine if a typespec, nested or otherwise, is a function
        function check_function_type(data) {
            if (typeof data == 'function'){
                return data();
            }
            return data;
        }
        
        //Compares input directly to spec
        function basicFilter(input, spec) {
            
                if (typeof input == typeof check_function_type(spec)){
                    return(input);
                } 
                if (typeof input != typeof check_function_type(spec)){
                    return(undefined);
                } 
        }
        
        function checkArrays(input, spec) {
                if (Array.isArray(input)) {
                    const output = input.filter(item => {
                        if (typeof item == typeof check_function_type(spec[0])) {
                            if (item == 0) {
                                return '0';
                            }
                            return item;
                        }
                    });
                    return(output);
                }
                else {
                    return(false);
                }
            }
        

        function checkObjects(input, spec) {
            if (input == null) {
                return undefined
            }
            if (typeof input == 'object' && input != null){
                const newObj = {}
                for (i in input) {    
                    if (typeof input[i] == typeof check_function_type(spec[i])) {
                        newObj[i] = input[i];
                    }
                }
                return(newObj);
            } else {
                return(false);
            }
            
        }
            

 }
}

Revision 1 is the official version created during exercise time limit
Revision 2 passes additional tests for arrays and objects
Revision 3 code is more modular and handles arbitrarily deep object