Assignment Functions JS

1. Create a Higher order function map, which takes two arguments
   1. An array: arr
   2. A callback function: cb
   3. The map function creates a new array with the results of calling a provided function on every element in the calling array.
   4. Example:
      1. function square(n) { return n * n; }
      2. var arr = [1, 2, 3, 4];
      3. var arrSquares = map(arr, square); // [1, 4, 9, 16]
2. Create a Higher order function filter, which takes two arguments
   1. An array: arr
   2. A callback function: cb
   3. The filter function creates a new array with all elements that pass the test implemented by the provided function.
   4. Example:
      1. function isEven(n) { return n % 2 == 0; }
      2. var arr = [1, 2, 3, 4];
      3. var arrEven = filter(arr, isEven); // [2, 4]
3. Create a Higher order function reduce, which takes three arguments,
   1. An array: arr
   2. A callback function: cb
   3. An initial value: init
   4. The reduce function applies a function against an accumulator and each element in the array (from left to right) to reduce it to a single value.
   5. Example:
      1. function sum(x, y) { return x + y; }
      2. var arr = [1, 2, 3, 4];
      3. var sum = reduce(arr, sum, 0); // 10
4. Create a Higher order function find, which takes two arguments
   1. An array: arr
   2. A callback function: cb
   3. The find function returns the value of the first element in the provided array that satisfies the provided testing function.
   4. Example:
      1. function isEven(n) { return n % 2 == 0; }
      2. var arr = [1, 2, 3, 4];
      3. var firstEven = find(arr, isEven); // 2
5. Create a Higher order function findIndex, which takes two arguments
   1. An array: arr
   2. A callback function: cb
   3. The findIndex function returns the index of the first element in the provided array that satisfies the provided testing function. If no values satisfy the testing function, -1 is returned.
   4. Example:
      1. function isEven(n) { return n % 2 == 0; }
      2. var arr = [1, 2, 3, 4];
      3. var firstEvenIndex = findIndex(arr, isEven); // 1
6. Create a Higher order function every, which takes two arguments
   1. An array: arr
   2. A callback function: cb
   3. The every function tests whether all elements in the array pass the test implemented by the provided function. It returns a Boolean value.
   4. Example:
      1. function isEven(n) { return n % 2 == 0; }
      2. var arr = [1, 2, 3, 4];
      3. var allEven = every(arr, isEven); // false
7. Create a Higher order function some, which takes two arguments
   1. An array: arr
   2. A callback function: cb
   3. The some function tests whether at least one element in the array passes the test implemented by the provided function. It returns a Boolean value.
   4. Example:
      1. function isEven(n) { return n % 2 == 0; }
      2. var arr = [1, 2, 3, 4];
      3. var someEven = some(arr, isEven); // true