Arrow functions application in JavaScript

Arrow functions have a particular advantage as callbacks. Let's look at an example of how much the code is simplified in this case. For example, let's say we have the following filter function with callback:

javascriptlet result = filter([1, 2, 3, 4, 5], function(elem) {
  if (elem % 2 === 0) {
    return true;
  } else {
    return false;
  }
});

First, let's get rid of the construction if and write the condition simply through the operator ===:

javascriptlet result = filter([1, 2, 3, 4, 5], function(elem) {
  return elem % 2 == 0;
});

Let us now replace the ordinary function with an arrow one:

javascriptlet result = filter([1, 2, 3, 4, 5], elem => elem % 2 == 0);

Задание 1

Given the following function with a callback:

javascriptlet result = every([1, 2, 3, 4, 5], function(elem) {
  if (elem > 0) {
    return true;
  } else {
    return false;
  }
});

Simplify the callback with an arrow function.

Задание 2

Given the following function with a callback:

javascriptlet result = every([1, 2, 3, 4, 5], function(elem, index) {
  if (elem * index > 10) {
    return true;
  } else {
    return false;
  }
});

Simplify the callback with an arrow function.

Задание 3

Given the following function with a callback:

javascriptlet arr = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];

let result = each(arr, function(elem, index) {
  if (elem * index > 10) {
    return true;
  } else {
    return false;
  }
});

Simplify the callback with an arrow function.