JavaScript Arrays 101

Topics to Cover

1. What arrays are and why we need them

2. How to create an array

3. Accessing elements using index

4. Updating elements

5. Array length property

6. Basic looping over arrays

What arrays are and why we need them

Arrays are datatypes in JavaScript (they are one of the most common data types in every programming language). They are like lists, and are used to store elements in a series or list format.

How to create an array

For example, if you want to make a list of grocery items, then, you can make an array like

let groceryList = ['apple', 'banana', 'potato'];

So, Arrays are nothing, but values stored in order.

Accessing elements using index

Now these values are usually called elements and these elements are accessible, by index.

Index is the place of element in Array. In JavaScript (and most other languages), Arrays are 0-based, i.e., apple is on 0 - index, banana is on 1 - index, and potato is on 2 - index.

So, groceryList[0] = apple
groceryList[1] = banana
groceryList[2] = potato

Now you can see it's easier than using 3 separate variables to store items

Updating elements

We can also update elements, simply by re-assigning them to different values.

groceryList[0] = 5;

So, now the first element is 5. Also, did you notice, in JS you can have elements of different types within same Array!.

Array length property

So, we can get length of an array using .length property.

For example, groceryList.length() will give 3, because there are 3 elements in groceryList.

Basic looping over arrays

So, we can loop over Arrays and perform operations like console.log, or multiplying each element by 2, etc.

So, yeah this was Arrays 101. Hope you enjoyed it.

Bye!