JacaScript Exercises, Practice, Solution

JacaScript Exercises, Practice, Solution.md

JavaScript Exercise[http://www.w3resource.com/javascript-exercises/]

JavaScript Functions

1. Write a JavaScript program to display the current day and time in the following format.

	var today = new Date();
	var day = today.getDay();
	var dayList = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'];
	console.log('Today is: ' + dayList[day]);
	var hour = today.getHours();
	var prepand = (hour >= 12) ? 'AM' : 'PM';
	if(hour > 12) {
		hour = hour - 12;
	}
	var min = today.getMinutes();
	var sec = today.getSeconds();
	console.log('Current time is: ' + hour + prepand + ':' + min + ':' + sec);

JavaScript Functions

1. Write a JavaScript function that reverse a number.

	function reverse(value) {
  		return parseInt(value.toString().split('').reverse().join(''));
	}
	OR
	function reverse(value) {
		var result = 0;
		var quotient = 0;
		var remains = 0;
		
		while(value > 0) {
			quotient = Math.floor(value / 10);
			remains = value % 10;
			result = result * 10 + remains;
			value = quotient;
		}
		
		return result;
	}

2. Write a JavaScript function that checks whether a passed string is palindrome or not?

	function checkPalindrome(strs) {
		if(strs === '') {
			return false;
		}
		
		var length = strs.length;
		var start = 0;
		var end = length - 1;
		
		while(start < end) {
			if(strs.charAt(start) != strs.charAt(end)) {
				return false;
				break;
			}
			start++;
			end--;
		}
		return true;	
	}

3. Write a JavaScript function that generates all combinations of a string.

    function combinations(str) {
        var final = [];
        var result = [];

        for(var i = 0; i < str.length; i++) {
            var currentChar = str.charAt(i);
            if(result.indexOf(currentChar) < 0) {
                var resultLength = result.length;
                for(var j = 0; j < resultLength; j++) {
                    result[j] = result[j].concat(currentChar);
                }
                result.push(currentChar);
                final = final.concat(result);
            }
        }
        return final;
    }

var TreeNode = function () { this.left = null; this.right = null; this.value = 0; };

var tree = new TreeNode(); tree.left = new TreeNode(); tree.right = new TreeNode(); tree.value = 10; tree.left.value = 1; tree.right.value = 2; tree.right.right = new TreeNode(); tree.right.right.value = 3; tree.right.left = new TreeNode(); tree.right.left.value = 4;

function sumNodes(rootNode) {
    
    if(rootNode.left == null && rootNode.right == null) {
        return rootNode.value;
    }
    if(rootNode.left != null && rootNode.right == null) {
        return rootNode.value + sumNodes(rootNode.left);
    }
    if(rootNode.left == null && rootNode.right != null) {
        return rootNode.value + sumNodes(rootNode.right);
    }
    return rottNode.value + sumNodes(rootNode.left) + sumNodes(rootNode.right);
}

5. Implement a function analyze(array, length) that has following functionalities. // Given any integer array e.g.

// int fred[]={1 2 3 5 7 2 7 4 11}; // analyze(fred,9);

// Analyze this simple data set and find the following quantities: // - minimum and maximum integer // - missing values within the range // - duplicated values and the number of duplicates // - mean of the values // - [do last] extra credit: standard deviation of the values

// example input and output:

// [devo]$ ./foo 1 2 3 5 7 2 7 4 11 // Min value is 1 // Max value is 11 // Mean value is 4.67 // Standard deviation is 3.20 // Integer 2 present 2 times // Integer 6 not present // Integer 7 present 2 times // Integer 8 not present // Integer 9 not present // Integer 10 not present

function analyze(array, length){
	var min = Min(array); // done
	var max = Max(array); // done
	var std = standardDeviation(array); // done
	var map = new Map();

	console.log('Min value is ' + min);
	console.log('Max value is ' + max);
	console.log('Standard deviation is ' + std);

	array.sort((a, b) => {
		return a - b;
	}); // done

	var index;
	var i;
	for(i = min; i <= max; i++) {
		if(array.includes(i)) {
			index = array.indexOf(i);
			while(i == array[index]){
				if(map.has(array[index])){
					map.set(array[index], map.get(array[index])+ 1);
				} else {
					map.set(i, 1);
				}
				index++;
			}	
		} else {
			map.set(i, 0);
		}
	}

	var iterator = map.entries();
	var current = iterator.next();
	while(current.done != true) {
		if(current.value[1] == 0) {
			console.log('Integer ' + current.value[0] + ' not present.');
		} else {
			console.log('Integer ' + current.value[0] + ' present ' + current.value[1] + ' times.');
		}
		current = iterator.next();
	}
}

function standardDeviation(values){
  var avg = average(values);
  
  var squareDiffs = values.map(function(value){
    var diff = value - avg;
    var sqrDiff = diff * diff;
    return sqrDiff;
  });
  
  var avgSquareDiff = average(squareDiffs);

  var stdDev = Math.sqrt(avgSquareDiff);
  return stdDev;
}

function average(data){
  var sum = data.reduce(function(sum, value){
    return sum + value;
  }, 0);

  var avg = sum / data.length;
  return avg;
}

function Min(array){
	var min = array[0];

	for(var index in array) {
		min = min < array[index] ? min : array[index];
	}

	return min;
}

function Max(array) {
	var max = array[0];
	for(var index in array){
		max = max > array[index] ? max : array[index];
	}
	return max;
}