JavaScript Exercises from 1 to 15

JavaScriptExercises.js

+//JavaScript Exercises:
+
+// “Hello, World!” printed
+
+console.log('Hello, World!')
+
+
+// 1. Reverse
+
+function reverse(string) {
+    let splitString = string.split(''); // to split the string letters into an array
+    let reverseLetters = splitString.reverse(); // to reverse the inicial array and save it in a variable
+    let joinString = reverseLetters.join(''); // to join the string back together 
+
+    return joinString;
+};
+
+console.log(reverse('Please!')); // !esaelP
+
+
+// 2. Factorial
+
+function factorial(n) {
+    if (n < 0) {
+        return 'n must be > or = to 0'; // for negative number
+    } 
+    else if (n == 0) {
+        return 1;      // for zero
+    }
+    else {
+         return (n * factorial(n - 1)); // for positive numbers
+    }
+};
+
+console.log(factorial(-6)); // n must be > or = to 0
+console.log(factorial(0)); // 1
+console.log(factorial(3)); // 6
+
+
+// 3. Longest Word
+
+function longest_word(sentence) {
+    const words = sentence.split(' ');
+    let longest = '';
+    for (i = 0; i < words.length; i++) {
+        if (longest.length < words[i].length) {  // compare strings and save on 'longest' the longest one
+            longest = words[i]; 
+        }                          
+    }     
+    return longest;
+};
+
+console.log (longest_word('The longest word works')); // longest
+
+
+// 4. Sum Nums
+
+function sum_nums(num) {
+    let sum = num; // inicialize sum 
+    let n = num; // inicialize n 
+    for (i = 0; i < num; i++) {
+        sum = sum + (n-1); // sum of previous numbers plus n-1
+        n = (n -1); // saving n-1 on n for the new cicle
+    }    
+    return sum;
+};
+
+console.log(sum_nums(5)); // 15
+
+
+// 5. Time Conversion
+
+function time_conversion(minutes) {
+    if (minutes >= 0) {
+        let hours = Math.floor(minutes/60); // separate hours from minutes after division for 60
+        let lastminutes = minutes - hours*60; // give the leftover minutes 
+        if (hours < 10) {
+            hours = `0${hours}`; // to put in the format 00:00
+        };
+        if (lastminutes < 10) {
+            lastminutes = `0${lastminutes}`; // to put in the format 00:00
+        };
+        return `${hours}:${lastminutes}`;
+    }
+};
+
+console.log(time_conversion(130)); // 02:10
+console.log(time_conversion(122)); // 02:02
+console.log(time_conversion(650)); // 10:50
+
+
+// 6. Count Vowels
+
+function count_vowels(string) {
+    str = string.toLowerCase();
+    let letters = str.split(''); // to split the string letters into an array
+    let count = 0;                  // inicialize a counter of vowels
+    for (i = 0; i < letters.length; i++) {
+        if (letters[i] == 'a' || letters[i] == 'e' || letters[i] == 'i' || letters[i] == 'o' || letters[i] == 'u') {
+            count = count + 1;       // if a vowel is found, counter receive +1
+        }     
+    }
+    return count;
+};
+
+console.log(count_vowels('HelloWorld')); // 3
+console.log(count_vowels("I'm home!")); // 3
+console.log(count_vowels('H A P P Y')); // 1
+
+
+// 7. Palindrome
+
+function palindrome(string) {
+    str = string.toLowerCase();
+    const splitString = str.split(''); // to split the string letters into an array
+    const reverseLetters = splitString.reverse(); // to reverse the inicial array and save it in a variable
+    const joinString = reverseLetters.join(''); // to join the string back together 
+    return str == joinString;
+};
+
+console.log(palindrome('day')); // false
+console.log(palindrome('Ana')); // true
+
+
+// 8. Most Letters
+
+function nearby_az(string) {
+    str = string.toLowerCase();
+    const splitString = str.split(''); // to split the string letters into an array
+    for (i = 0; i < splitString.length; i++) {
+        return (splitString[i] == 'a' && (splitString[i+1] == 'z' || splitString[i+2] == 'z' || splitString[i+3] == 'z'))
+    }; // return (true) if a letter “z” appears within three letters after an “a” 
+};
+
+console.log(nearby_az('az')); //true
+console.log(nearby_az('arrrrz')); // false
+console.log(nearby_az('allez')); // false
+console.log(nearby_az('arrz')); // true
+
+
+// 9. Two Sum
+
+function two_sum(nums) {
+    let positions = [];
+    for (i = 0; i < nums.length; i++) {
+        for (j = i+1; j < nums.length; j++) {
+            if (nums[i] + nums[j] === 0) {
+                positions.push(i,j);
+            };
+        };
+        
+    };
+    if (positions.length == 0) { 
+        return null;
+    }
+    else {
+        return positions;
+    }  
+};
+
+console.log(two_sum([1, 3, -1, 5])); // [[0, 2])
+console.log(two_sum([1, 3, -1, 5, -3])); // [[0, 2], [1, 4]]
+console.log(two_sum([1, 5, 3, -4])); // null
+
+
+// 10. Is Power of Two
+
+function is_power_of_two(num) { // didn't considered negative numbers for exponent (ex: 2⁻² or 2⁻⁵)
+    if (num <= 0) {return false}; // impossible
+    while ((num%2) == 0) { // while the rest of the division is 0 keep dividing
+        num = num/2;
+    } 
+    return num == 1; // if the final number after the divisions is 1 return true (it's a power of 2)    
+};
+
+console.log(is_power_of_two(16)); // true
+console.log(is_power_of_two(6)); // false
+console.log(is_power_of_two(8)); // true
+console.log(is_power_of_two(0)); // false
+
+
+// 11. Repeat a string
+
+function repeat_string_num_times(str, num) {
+    if (num > 0) {                  // return an empty string if num is not a positive number
+        const string = str.repeat([num]);
+        return string;
+    }
+    else {                      
+        return '';
+    }
+};
+
+console.log(repeat_string_num_times('123', 0)); // ''
+console.log(repeat_string_num_times('abc', 2)); // abcabc
+console.log(repeat_string_num_times('abc', -2)); // ''
+console.log(repeat_string_num_times('ho', 4)); // hohohoho
+
+
+// 12. Sum All Numbers in a Range
+
+function add_all(arr) {     // assumed that will only be passed arrays with 2 numbers
+    let firstnumber = arr[0]; 
+    const secondnumber = arr[1];
+    let sum = 0;
+    while (firstnumber <= secondnumber) { // while the first number is <= then the second number, add it to the sum 
+        sum = sum + firstnumber;
+        firstnumber = firstnumber + 1;
+    };
+    return sum;
+};
+
+console.log(add_all([2,5])); // 14
+console.log(add_all([-2,1])); // -2
+console.log(add_all([0,0])); // 0
+
+
+// 13. True or False
+
+function is_it_true(args) {
+   if(typeof(args) === "boolean") {  // check if the type of the argument is a boolean
+       return true;
+   }
+   else {
+       return false;
+   }
+};
+
+console.log(is_it_true('false')); // false
+console.log(is_it_true(false)); // true
+console.log(is_it_true(1)); // false
+console.log(is_it_true(true)); // true
+
+
+// 14. Return Largest Numbers in Arrays
+
+function largest_of_four(arr) {
+    
+    
+    if (arr.length === 0) {
+        return 'The array is empty'; // in case it's passed an empty array
+    }
+    else {
+        let largestnumbers = 0; // works only for an array with at least 1 positive number
+        let finalnumbers = []; 
+        for (i = 0; i < arr.length; i++){ // for each array inside the inicial array 
+            largestnumbers = 0;
+            for (j = 0; j < arr[i].length; j++) { // inside each individual array
+                if (arr[i][j] > largestnumbers) {
+                    largestnumbers = arr[i][j];
+                }
+            }
+            finalnumbers.push(largestnumbers); // new array with the largest numbers of each individual array inside the inicial one
+        }
+        return finalnumbers;  
+    }
+};
+
+
+console.log(largest_of_four([[13, 27, 18, 26], [4, 5, 1, 3], [32, 35, 37, 39], [1000, 1001, 857, 1]])); // [27,5,39,1001]
+console.log(largest_of_four([[-1, -5, -12, 2], [0, 1, 57, 0]])); // [2, 57]
+
+
+// 15. Is it an anagram?
+
+function isAnagram(test, original) {
+    if (test.length != original.length) {
+        return false
+    }
+    else{
+        return test.toLowerCase().split('').sort().join() === original.toLowerCase().split('').sort().join(); 
+    } // strig to lower case, split the string in letters into an array, sort array alphabetically, join it back into a string
+};
+
+console.log(isAnagram('foefet', 'toffee')); // true
+console.log(isAnagram('days', 'aDys')); // true 
+console.log(isAnagram('huhuhu', 'huhu')); // false

helloworld.js

-console.log('Hello, World!')