Homework for 270218

js/findLongestWord.js

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+// Write a function findLongestWord that takes an array of words and returns the length of the longest word in the array.
+
+function findLongestWord(arr) {
+    var longest = 0;
+    for (var i = 0; i < arr.length; i++) {
+        if (arr[i].length > longest) {
+            longest = arr[i].length;
+        }
+    }
+    return longest;
+}
+
+
+console.log(findLongestWord(["aa","bbb","cccc"]) === 4);

js/isCharacterAVowel.js

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+// Write a function isCharacterAVowel that takes a character (i.e. a string of length 1) and returns true if it is a vowel and false, otherwise.
+
+function isCharacterAVowel(char) {
+    vowels = ['a','e','i','o','u','A','E','I','O','U']
+    if (vowels.includes(char)) {
+        return true;
+    }
+    return false;
+}
+
+console.log(isCharacterAVowel("a") === true)
+console.log(isCharacterAVowel("A") === true)
+console.log(isCharacterAVowel("4") === false)
+console.log(isCharacterAVowel(0) === false)

js/isPrime.js

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+// Create a function to return true or false if a number passed in a prime number.
+
+function isPrime(num) {
+    // for special cases of 1 and 2
+    if (num === 1) {
+        return false;
+    }
+    if (num === 2) {
+        return true;
+    }
+    // start evaluating a number from its square to reduce number of computations
+    var newNum = Math.ceil(Math.sqrt(num));
+
+    // if the number is divisible by anything other than 1, it is not an integer
+    for (var i = newNum; i > 1; i--) {
+        if (Number.isInteger(num/i)) {
+            return false;
+        }
+    }
+    return true;
+}
+
+console.log(isPrime(1) === false);
+console.log(isPrime(2) === true);
+console.log(isPrime(541) === true);
+console.log(isPrime(4) === false);

js/letterCount.js

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+// Write a function that takes a string that finds out how many times a character occurs. For example, the string "apple" would print the following:
+
+// a - 1
+// p - 2
+// l - 1
+// e - 1
+// Hint: Loop through each letter, and increment the value to a key in an object. The key should be that object.
+
+// BONUS: Make sure that lower case letters and upper case letters count for the same character. Also, ignore spaces and punctuation.
+
+function letterCount(word) {
+    var letters = {};
+    word = word.toLowerCase().replace(/\s/g, ''); // strip white space and lowercase letters
+
+    for (var i = 0; i < word.length; i++) {
+        var letter = word[i];
+        if (letters[letter]) {
+            letters[letter] += 1;
+        }
+        else {
+            letters[letter] = 1;
+        }
+    }
+    for (var letter in letters) {
+        console.log(letter + " - " + letters[letter]);
+    }
+}
+
+
+
+letterCount("apple");
+letterCount("apPle");
+letterCount("apple ");
+letterCount("apple APPLE");

js/maxOfThree.js

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+// Define a function maxOfThree that takes three numbers as arguments and returns the largest of them. Use the if-then-else construct available in Javascript.
+
+function maxOfThree(num1, num2, num3) {
+    var bigNum = num1; 
+    if (num2 > bigNum) {
+        bigNum = num2;
+    }
+    if (num3 > bigNum) {
+        bigNum = num3;
+    }
+    return bigNum;
+}
+
+console.log(maxOfThree(3, 1, 2))
+console.log(maxOfThree(4, 15, 23))
+console.log(maxOfThree(3, 100, 20))

js/merge.js

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+// Write a function called merge. The function should take two sorted arrays of numbers as input and return a merged array of the sorted numbers from the input. For example, if the input arrays were var arr1 = [3,6,11]; var arr2 = [2,4,5,8,9]; Then the returned array would be: [2,3,4,5,6,8,9,11].
+
+function merge(arr1, arr2) {
+    var arr3 = [];
+    var totalCount = arr1.length + arr2.length;
+
+    for (var i = 0; i < totalCount; i++) {
+        if (arr1.length === 0) {
+            arr3 = arr3.concat(arr2);
+            break;
+        }
+        if (arr2.length === 0) {
+            arr3 = arr3.concat(arr1);
+            break;
+        }
+        var num1 = arr1[0];
+        var num2 = arr2[0];
+        if (num1 < num2) {
+            arr3 = arr3.concat(arr1.shift());
+        }
+        else {
+            arr3 = arr3.concat(arr2.shift());
+        }
+    }
+    return arr3;
+}
+
+console.log(merge([3,6,11],[2,4,5,8,9]))

js/primes.js

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+// Using your isPrime() function, create a function primes that will return an array of all prime numbers up to a certain amount.
+
+function isPrime(num) {
+    // for special cases of 1 and 2
+    if (num === 1) {
+        return false;
+    }
+    if (num === 2) {
+        return true;
+    }
+    // start evaluating a number from its square to reduce number of computations
+    var newNum = Math.ceil(Math.sqrt(num));
+
+    // if the number is divisible by anything other than 1, it is not an integer
+    for (var i = newNum; i > 1; i--) {
+        if (Number.isInteger(num/i)) {
+            return false;
+        }
+    }
+    return true;
+}
+
+function primes(limit) {
+    var count = 0;
+    // check positive integers only
+    for (i = 1; i <= limit; i++) {
+        if (isPrime(i)) {
+            count++;
+        }
+    }
+    return count;
+}
+
+console.log(primes(10) === 4);
+console.log(primes(1000) === 168);
+

js/reverseString.js

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+// Define a function reverseString that reverses a string. For example, reverseString("jag testar") should return the string "ratset gaj".
+
+function reverseString(str) {
+    var reversed = "";
+    for (var i = 0; i < str.length; i++) {
+        reversed += str[str.length - 1 - i];
+    }
+    return reversed;
+}
+
+console.log(reverseString("jag testar") === "ratset gaj");

js/sillySum.js

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+// Write a function that takes an array of numbers, and returns the sum of each number multiplied by its index.
+
+function sillySum(arr) {
+    var sum = 0;
+    for (var i = 0; i < arr.length; i++) {
+        sum += arr[i] * i;
+    }
+    return sum;
+}
+
+console.log(sillySum([2,5]) === 5);
+console.log(sillySum([1,2,3]) === 8);

js/sumArray.js

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+// Define a function sumArray and a function multiplyArray that sums and multiplies (respectively) all the numbers in an array of numbers. For example, sumArray([1,2,3,4]) should return 10, and multiplyArray([1,2,3,4]) should return 24.
+
+function sumArray(arr) {
+    var sum = 0;
+    for (var i = 0; i < arr.length; i++) {
+        sum += arr[i];
+    }
+    return sum;
+}
+
+function multiplyArray(arr) {
+    var mult = 1;
+    for (var i = 0; i < arr.length; i++) {
+        mult *= arr[i];
+    }
+    return mult;
+}
+
+console.log(sumArray([1,2,3,4]) === 10);
+console.log(multiplyArray([1,2,3,4]) === 24);