curriculum/challenges/english/blocks/lecture-working-with-arrays/6732aebaa8abb9086a9bb17a.md
In the previous lesson, you were first introduced to working with arrays and accessing different elements from arrays. Here is a reminder on how to access the second element from an array:
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const fruits = ["apple", "banana", "cherry"];
console.log(fruits[1]); // "banana"
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Since arrays are zero based indexed, the first element will be at index 0, the second index will be at index 1, etc. It's important to note that if you try to access an index that doesn't exist in the array, JavaScript will return undefined.
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let fruits = ["apple", "banana", "cherry"];
console.log(fruits[3]); // undefined
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In this example, there is no index 3 for the fruits array. So the log will show undefined. Now, let's look at how to update elements in an array. You can update an element by assigning a new value to a specific index.
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let fruits = ["apple", "banana", "cherry"];
fruits[1] = "blueberry";
console.log(fruits); // ["apple", "blueberry", "cherry"]
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In this example, we've replaced banana with blueberry at index 1. This method allows you to change any element in the array, as long as you know its index. You can also add new elements to an array by assigning a value to an index that doesn't yet exist:
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let fruits = ["apple", "banana", "cherry"];
fruits[3] = "date";
console.log(fruits); // ["apple", "banana", "cherry", "date"]
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However, exercise caution when doing this. If you assign a value to an index that is much larger than the current length of the array, you will create undefined elements for the indices in between, which can lead to unexpected behavior. As you continue to work with JavaScript, you'll find that these ways of accessing and updating array elements are fundamental to many programming tasks. Whether you're building a simple todo list or processing complex data structures, these skills will be invaluable.
If you have an array let numbers = [10, 20, 30, 40, 50], what will numbers[2] return?
20
Remember that array indexing starts at 0.
30
40
Remember that array indexing starts at 0.
2
Remember that array indexing starts at 0.
2
What happens if you try to access an array element at an index that doesn't exist?
It throws an error.
Think about what JavaScript does when it can't find a value at a specified index.
It returns null.
Think about what JavaScript does when it can't find a value at a specified index.
It returns undefined.
It returns the last element of the array.
Think about what JavaScript does when it can't find a value at a specified index.
3
What is the index number used to represent the first element of an array?
5
Remember we don't start counting at 1. We start counting at a different number when dealing with arrays.
2
Remember we don't start counting at 1. We start counting at a different number when dealing with arrays.
0
1
Remember we don't start counting at 1. We start counting at a different number when dealing with arrays.
3