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Iterators
The .map() Method

The second iterator we’re going to cover is .map(). When .map() is called on an array, it takes an argument of a callback function and returns a new array! Take a look at an example of calling .map():

const numbers = [1, 2, 3, 4, 5]; const bigNumbers = numbers.map(number => { return number * 10; });

.map() works in a similar manner to .forEach()— the major difference is that .map() returns a new array.

In the example above:

  • numbers is an array of numbers.
  • bigNumbers will store the return value of calling .map() on numbers.
  • numbers.map will iterate through each element in the numbers array and pass the element into the callback function.
  • return number * 10 is the code we wish to execute upon each element in the array. This will save each value from the numbers array, multiplied by 10, to a new array.

If we take a look at numbers and bigNumbers:

console.log(numbers); // Output: [1, 2, 3, 4, 5] console.log(bigNumbers); // Output: [10, 20, 30, 40, 50]

Notice that the elements in numbers were not altered and bigNumbers is a new array.

Instructions

1.

Add your code under the animals array and before the line console.log(secretMessage.join(''));

Use .map() to create a new array that contains the first character of each string in the animals array. Save the new array to a const variable named secretMessage.

2.

Use .map() to divide all the numbers in bigNumbers by 100. Save the returned values to a variable declared with const called smallNumbers.

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