Challenges in a hard way

quizez.js

// Find summ of all elements in array => result: 32
var multiArr = [1, '2x', ['3', ['x2', ['10', '10'], '5'], '1x']];

function summ(arr, result) {
	var result = result || 0;

	for (var i = 0; i < arr.length; i++) {
		var number = arr[i];
		var notNumber = isNaN(parseInt(number));
		var isArray = Object.prototype.toString.call(number) === '[object Array]';

		if(!isArray && !notNumber) {
			result += parseInt(number);
		}
		else if(isArray) {
			result = summ(number, result);
		}
	}

	return result;
}

summ(multiArr);

// Merge letters with defined separator in first argument => result: 'a,b'
function mergeLetters(args) {
	if (!arguments || arguments.length < 2) {
		throw('Pass delimiter and letters');
	}

	var args = Array.prototype.slice.call(arguments);
	var delimiter = args.splice(0,1)[0];

	return args.join(delimiter);
}

mergeLetters(',', 'a', 'b');

// Compress letters by occurencies => result: A4B3C2XYZD4E3F3A6B28
var letters = 'AAAABBBCCXYZDDDDEEEFFFAAAAAABBBBBBBBBBBBBBBBBBBBBBBBBBBB';

function runLengthEncoding(str) {
    if (str.length === 0 || Object.prototype.toString.call(str) !== '[object String]') {
        throw('Invalid data');
    }

    var occurencies = 1;
    var result = '';
    
    for (var i = 0; i < str.length; i++) {
        var char = str.charAt(i);
        var nextChar = str.charAt(i + 1);
       
        if (char === nextChar) {
            ++occurencies;
        } else {
            result += occurencies === 1 ? char : (char + occurencies);
	    occurencies = 1;
        }           
   }
    
    return result;
}

runLengthEncoding(letters);

// Detect whether word or phrase is palindrome
var latinWord = 'A man, a plan, a canal -- Panama';
var cyrWord = 'Око';

function isPalindrom(str) {
	if (!str || Object.prototype.toString.call(str) !== '[object String]') {
		throw('Pass valid string');
	}
	
	var clearedString = str.replace(/[^a-z\u0400-\u04FF]/gi, '').toLowerCase();
	var middle = Math.floor((clearedString.length - 1) / 2);
	var index = 0;

	while(index <= clearedString.length - 1) {
		var prev = clearedString.charAt(middle-index);
		var next = clearedString.charAt(middle+index);

		if(prev !== next) {
			return false;
		} 
		else {
			++index;
		}
	}

	return true;
}

isPalindrom(word);

function flattenFilesystem(fs, output = [], dir) {
	return fs.reduce((acc, item) => {
		const isString = Object.prototype.toString.call(item) === '[object String]';
		const isObject = Object.prototype.toString.call(item) === '[object Object]';
        	const rootPath = dir ? `${dir}/${item}` : item;

		if (isString) {
			acc.push(rootPath);
		} else if(isObject) {

			Object.keys(item).forEach((key) => {
                		let path = dir ? `${dir}/${key}` : key;
				
                		if (Array.isArray(item[key])) {
					flattenFilesystem(item[key], output, path)
				} else {
                    			path = dir ? `${dir}/${key}/${item[key]}` : item[key];
					acc.push(path);
				}
			});
			
		}

		return acc;
	}, output);
};

const fileStructure = [
    'a.js',
    'b.js',
    null,
    false,
    {
        src: [
        	'index.js',
		{
		    js: [
			'Home.js',
		    	'About.js',
		    ],
		    assets: [
			{sprites: ['sprite.svg']},
		    	'icons.svg',
		    ]
		}
        ]
    },
    {
        routes: [
            'index.js'
        ]
    }
];

flattenFilesystem(fileStructure);

// Spread any type
function spreadAny(arr, arguments) {
	return [...arr, ...[arguments]];
}